The Best Motor Oil for the Average Car

When buying motor oil, I typically choose whichever synthetic is currently on sale, taking care to use the correct viscosity for my particular car, and I stick with a familiar brand. If nothing is on sale, I’d go with Mobil 1 because it’s a reliable brand with a solid track record for providing excellent engine protection, and it’s on the tip of the tongue of every expert I spoke with.

But above all else, make sure you change your oil regularly, following the recommendations in your owner’s manual. The greatest oil in the world eventually fills with contaminants and breaks down from heat and friction. Failure to change the oil in your engine regularly will eventually cause serious damage (and void your warranty).

Motor oil is a tough subject because of the complex chemistry involved and the difficulty seeing the actual effects of different formulations or brands. People can be pretty passionate about their favorite brands, too. To solve this puzzle, I threw out everything I thought I knew about oil and spent two weeks thinking about little else. I read reviews and evaluations from magazines and consumer groups, then consulted with techs at oil manufacturers and labs that perform oil analysis. I talked to mechanics who see the effects of oil use and misuse on every possible make and model of car. I even spoke to veteran race engine builder Ron Hutter.

The fact is, there’s very little difference between different brands of motor oil.
The fact is, there’s very little difference between different brands of motor oil. Consumer Reports said as much in 2010: “The brand of motor oil matters little, but its viscosity grade (10W-30, for example) is important. Use only what the owner’s manual specifies. Using the wrong [viscosity] oil can lead to reduced lubrication and shorter engine life. If the manual says to use synthetic oil, do so. Contrary to what some believe, adding a synthetic oil to regular oil won’t harm the engine, but there’s also no benefit in doing so.”

Blackstone Laboratories has been testing motor oil using inductive coupled plasma spectrometry since 1985. I asked company president Ryan Stark if he’d seen any oils that performed consistently better or worse, based on his test results. “No. If you stick with a name brand oil, you really can’t go wrong. If you did a side by side test between two brands you might see a 1 or 2 parts per million difference in the metals in the results.”

Royal Purple manufactures what they call “super-premium motor oils for consumer use.” From the company’s origins in the 1980s as a developer of industrial lubricants, they expanded into racing oil and eventually consumer motor oil in 2003. Jim Morrissey, a junior automotive technical support engineer with Royal Purple, was candid about the challenges in evaluating motor oils when I asked him how a consumer could choose between two oils on a store shelf. “That’s one of the difficulties, actually. There are ways of determining a minimum standard, like the API certification, but when you’re dealing with a premium product, there really is no third party available to evaluate the product. Sometimes a magazine or TV show will do a side-by-side analysis, but it’s pretty much up to the consumer. Determining which is ‘the best’ can be nebulous. It depends what you’re looking for.”

Even Valvoline’s own FAQ for their synthetic SynPower has a hard time coming up with any appreciable differences between brands: “How does Valvoline SynPower compare to Mobil1 and Amsoil? Valvoline’s SynPower synthetic motor oils meet and exceed the same specifications as these two products.” Not exactly a ringing endorsement.

I spoke with Bob Gugino, owner of Bison Automotive in Kenmore, NY (he’s the guy I take my car to when it’s a problem I can’t fix myself). Bob’s been a mechanic for 35 years. He told me, “As far as brand names, Valvoline, Mobil, Castrol, there’s not a whole lot of difference between them. They all make a lot of claims, that their oil is better at this or that, but they all have to meet a certain spec.”

I also spoke with Kevin Knox, an auto technician at Mullane Motors in Lockport, NY with 30 years of experience. Because he works at a dealership that also sells used cars, Knox has been under the hood of many different makes and models of cars. “A lot of people have preferences, I don’t know if one brand is superior. I look at the requirements of the vehicle.”

Even on internet forums dedicated to motor oil, where people can get downright religious about their favorite brands, you’ll find plenty of “oil is oil” advice. A user named SteveSRT8 at the Bob is the Oil Guy forum said in 2012, “Seriously, we run a fleet with all 6.0 [liter engines] and a few 5.3s and they run nearly forever. Our secret? Pick whatever synthetic is on sale and change when the OLM says to. Pretty simple. And we have as severe a duty cycle as anything in the entire world.”

So why Mobil 1?

First, let me tell you something about oil.

All motor oils sold in the U.S. are tested by the American Petroleum Institute (API). If the oil meets certain minimum qualifications, the manufacturer can place the API star logo on the package. I’m not sure if it’s even possible to find non-API approved oil on store shelves. Also check the API “donut” that appears next to the star. It should have the letters “SM” on it, designating the latest API oil category specification, designed for modern engines. Again, it’s actually difficult to find oil that doesn’t carry the SM designation—a few specialty manufacturers produce oils for classic cars that have oil requirements not met by modern formulations, so you may occasionally come across “SF” oil or another designation.

I’m not sure if it’s even possible to find non-API approved oil on store shelves.
As long as the oil packaging carries those two logos, you can be sure the oil meets the API’s minimum performance requirements, even if it’s an inexpensive “off-brand” oil. However, some of the mechanics I spoke to were wary of generic oils. Kevin Knox said, “If you see some generic oil at one of the big box stores, even if it meets the SAE [Society of Automotive Engineers, which conducts oil viscosity tests] rating, it might not be as good, it might not have the same lubricating qualities and resistance to heat and pressure. It’s not worth saving 50 cents or 75 cents a quart.”

If you keep an eye on Amazon for sales, watch for rebates at manufacturer websites, or spot a sale at your local auto parts store or Wal-Mart, you can get popular oil brands for prices as low as $3 per quart for conventional oil and under $10 per quart for synthetics.

If you’re looking for oil that meets some kind of performance test that sets a higher bar than the API logo, you might look for General Motors’ Dexos certification. An oil carrying the Dexos logo meets a more stringent set of requirements. However, note that GM requires oil manufacturers to pay a licensing fee to carry the Dexos logo. Not all manufacturers pay for the licensing. For instance, in a 2011 interview with Edmunds, a Valvoline representative said, “Our SynPower 5W-20, 5W-30 and DuraBlend 5W-30 went through all the Dexos testing and passed all the requirements. But we felt that carrying the Dexos name was not providing the consumer with any value.”

Why is Mobil 1 my pick, price notwithstanding? I asked Philip Reed, senior consumer advice editor for, if there are appreciable differences between brands of motor oil. He said, “Keep in mind that most conventional oils are now using some percentage of synthetic. So the line between synthetic and non-synthetic is becoming blurred. Also keep in mind that oil chemistry in all oils is vastly improved in recent years. So if you stick with the name brands, you can’t go too far wrong…In most cases we just tell people to follow the guidelines in the owner’s manual. However, as cars get older the manual is less useful and the maintenance becomes even more important. This doesn’t mean more frequent oil changes but perhaps checking oil level more often. With that in mind, I’d have to say that Mobil seems most active in offering a wide range of oils for a range of cars of different ages.”

Mobil 1 holds a 4.4 out of five aggregate rating at Amazon, with 24 5-star reviews out of 34 total. While it’s difficult for the end user to really see the difference motor oil makes, reviewers tell some convincing tales of trouble free long-term use, which is what you really want out of a motor oil. Reviewer loustorm says, “I used to work at Aberdeen Proving Ground where, among other things, Army vehicles are tested. I learned that Mobil 1 was given a top rating. That’s all I use now.” Steven E. Snyder tells the tale of a Camaro filled with Mobil 1 that drove for several weeks with a faulty oil pump, concluding, “Even with little/no oil pump the car never locked up. Mobil 1 isn’t half-bad.”

Few other oils have the robust record of Amazon reviews that Mobil 1 enjoys. Valvoline Synpower 5W-40 has a 4.5 star average on 28 total reviews, which is certainly on par with Mobil 1. That particular formulation seems to find favor with owners of European-built or designed engines. “I have been using this oil in both of my Audis for several years and have put on thousands of miles with no engine lubrication issues. My older A4 has over 250,000 miles and still runs strong with only slight oil consumption between 5000 mile oil changes. My newer A4 does not use a drop between changes at 5000 miles. I have been very pleased with this oil and would recommend it to anyone that requires a 5W-40 for their Euro built vehicle,” said khubbard1.8T in 2012.

Royal Purple 5W-30 also has a 4.5 average on 87 reviews, but many of them parrot marketing hype or make ridiculous claims, like one reviewer who swears the oil caused his Mini Cooper to do a burnout. There are also a lot of reviews that acknowledge that Royal Purple is a fine synthetic oil, but seem put off by the higher price and marketing hype (note that, as I write this, Royal Purple is actually slightly cheaper than Mobil 1 at Amazon, but the prices shift frequently, not even counting sales and rebates). User trarmour is typical: “I have previously been using Mobil 1 in all of my vehicles and boats. Royal Purple claims of ‘feel the performance’ as well as improved mileage and more horse power. I didn’t receive any of that! I’m a certified GM technician and this is good oil however it is ‘just another synthetic.’ It’s not the ‘magical mystery oil’ Royal Purple claims. Not worth the additional cost in my opinion.”

Mobil 1 is used as the factory fill engine oil for all Chevrolet Corvettes, some Camaros, all Mercedes AMG cars, all cars made by Porsche, and specific models made by Holden, Acura, Nissan, Lexus, McLaren and others. That information certainly should be taken with a grain of salt—factory fill agreements can be as much the result of business partnerships and co-branding as oil performance. That still leaves the fact that Porsche trusts Mobil 1 enough to put it in all of their cars. Of course, each oil manufacturer has similar endorsements. Castrol is used as the factory fill by BMW, for example.

Sean Hixson, a public relations supervisor for Mobil 1, provided a few examples of Mobil 1 holding up under extreme conditions. “In a controlled wear protection test using a 2010 Honda Accord LX 4-cylinder, after 105,000 miles with 15,000-mile oil change intervals using Mobil 1 advanced fully synthetic oil, most engine parts were still within new engine tolerances. In a high-performance Chevrolet Camaro SS, our engineers tested Mobil 1 synthetic oil in the Camaro’s V-8 running at 25,000 mile oil change intervals—two to three times longer than recommended by Chevrolet—and found there was excellent engine cleanliness and no noticeable engine wear.”

If that seems like a pretty weak endorsement of Mobil 1 as the “best” motor oil, that’s intentional.
Those results come with a big caveat, though: they’re basically impossible to verify, and every oil manufacturer makes similar claims. Amsoil, for instance, features a testimonial on their website about a 1968 Plymouth Barracuda that’s pushing 500K miles thanks to the wonders of Amsoil products. It’s excerpted from an article in Hemmings Classic Car magazine, and the car’s owner turns out to be an Amsoil dealer. “Garner said the reason the engine has lasted nearly a half-million miles without requiring any major work other than a valve job is because he has been using AMSOIL synthetic oil since the mid-1970s. ‘I understood AMSOIL was one of the best products out there,’ Garner said. ‘It seems to be true because the inside of the old 318 (cubic inch, V-8) still looks clean, with no varnish or sludge anywhere.'” But Garner also follows a strict and thorough maintenance schedule for his ‘Cuda, so it’s impossible to chalk the durability solely up to the oil.

Castrol claims superiority in a number of categories, based on their own internal testing, noting in one promotional video, “Castrol Edge with Syntec Power technology 5W-30 was proven stronger based on Castrol’s extreme test of maximum torque, strength and endurance versus Mobil 1 5W-30.” In another video, Castrol engineers extoll the virtues of their proprietary testing: “It’s been tested in some very specific and demanding tests that we have designed, such as the fluid strength test and the maximum endurance test. We have superior performance in the industry tests, superior performance in the OEM tests, but we will even invent tests that go beyond anything that’s looked at, and we will do well in our own proprietary tests.”

Pennzoil emphasizes their synthetic oil’s ability to reduce piston deposits, citing their performance in the American Society for Testing and Materials (ASTM) Piston Deposit Test. “Actual advantage over competition: Pennzoil Platinum keeps pistons up to 8% cleaner than Mobil 1; up to 17% cleaner than Valvoline SynPower; and up to 20% cleaner than Castrol Edge with Syntec.” Of course, reducing piston deposits is only one element of an oil’s performance.

The fact that every oil manufacturer can make these claims underscores the overall quality you’ll find in modern oils regardless of brand. While I think Mobil 1 is a safe choice to fall back on, if you can find another established brand of synthetic oil at a cheaper price, it will work just as well. If that seems like a pretty weak endorsement of Mobil 1 as the “best” motor oil, that’s intentional.

Picking a viscosity

The array of oil varieties looks bewildering at first, but breaking down the decision into steps makes it a lot more manageable. First you need to know what viscosity is appropriate for your car. That’s the “5W-30″ number you’ll see on the oil bottle. The two numbers refer to the oil’s viscosity properties during a cold start (the W stands for “winter”) and at high operating temperatures. Luckily, you don’t need to understand those numbers in any way. Just buy whatever your owner’s manual tells you to buy. It will clearly indicate what viscosity is required for your particular engine. If you’ve misplaced your owner’s manual, you can probably find it online.

Conventional versus synthetic

The next decision is whether to buy conventional or synthetic oil. The owner’s manual might help out here, too—some cars require synthetic oil, or require an oil viscosity that only comes in synthetic oils (like 0W-20). If the manual doesn’t demand synthetic, you still might want to use a synthetic oil under certain circumstances:

  • Turbocharged or supercharged engines.
  • High-performance engines.
  • Engines that are frequently pushed hard.
  • Engines that do a lot of towing or hauling heavy loads.

Let’s say you’re on the fence about whether you should use conventional or synthetic oil. What’s the difference? Conventional oil is made from petroleum that comes out of the ground and is refined until it has the appropriate qualities for a motor oil. Various additives, like detergents, viscosity index improvers, and rust inhibitors, are then mixed in. Synthetic oils are built from designer molecules (which are still derived from petrochemicals) to have the exact qualities the manufacturer wants. They’re mixed with additives too.

Amazon’s product description, which they include for all synthetic oils, actually does a very good job of explaining the differences: “This oil is a full synthetic oil, meaning crude oil is not used in making it. Synthetic oil can be used in vehicle engines instead of motor oils refined from crude oil, and often provides superior mechanical performance over traditional motor oil, including increased gas mileage and reduced engine wear at extreme temperatures. Its complex method of production means it can often cost more than conventional motor oil.”

The base stocks that oils are made from are divided into groups, so you may hear gearheads talking about “Group IV vs. Group V synthetics,” which is based on whether the oil is derived from polyalphaolefins (PAO) or esters. Esters (Group V) are considered “better,” but for the end user, you’re more interested in how the final oil product performs than what base stocks were used. Oil manufacturers tend to not reveal exactly what combination of base oils were used to create their synthetic oils, so it’s difficult to base your purchase on this factor.

When I started researching  this article, I figured synthetic oils were all marketing hype, and you could get by on conventional stuff. There certainly is plenty of marketing hype to go around in the motor oil business. But there is consensus that synthetics do offer better protection. The more extreme the conditions that the engine runs under, or the tighter the tolerances on that engine, the more a synthetic oil is going to shine.

In terms of raw numbers, synthetic oils hold a few advantages over conventional oils. According to Marlan Davis of Car Craft, a synthetic oil will still flow at temperatures more than 20 degrees Fahrenheit colder than the point where a conventional oil becomes too cold to lubricate the engine at startup.

There is consensus that synthetics do offer better protection.
Bob at Bison Automotive told me that he’d recommend synthetic oil if the manufacturer requires it, if the car is subject to heavy use, like driving lots of miles in a short time, or if you plan on keeping the car for many years. Unless you’re leasing, I think most of us plan to keep our cars for a lot of years. “We’ll use a synthetic oil on a high performance vehicle, like a Viper,” said Kevin Knox. “The manufacturer is usually going to specify a synthetic for those because it holds up better under pressure.”

Mike Allen, senior editor at Popular Mechanics, summarized the synthetic versus conventional debate in a 2007 article. “Some high-performance and high-end cars come factory filled with synthetic, and you should stick with it. If you live where it gets really frigid in the winter, you might be better off with a synthetic for its superior cold-weather starting. If you tow a trailer and your oil temperature is consistently above 200 F, you should use a synthetic oil and install an auxiliary oil cooler…If your driving cycle or your vehicle is more average, you probably can drive your car well past 200,000 miles without needing major engine work by using the proper grade of conventional mineral oil and appropriate change intervals.”

The final word on when to use synthetic oil comes from Ron Hutter. Hutter has been building racing engines for NHRA pro stocks and NASCAR modifieds since the 1970s, and built the engines that powered Dale Earnhardt, Jr. to a pair of Busch (now Nationwide) Series championships in 1998 and 1999. “Well, my regular car is a ’98 Cadillac with over 90,000 miles on it,” he told me. “I’m not too particular about what I put in that. But we have an ’06 Corvette, and we use synthetic oil in that.”

What a synthetic oil won’t do is give you any kind of noticeable performance boost at the gas pedal, despite manufacturer claims that they will. Yes, the superior lubricity and resistance to losing viscosity at high temperatures may give you a few extra horsepower. Under dynamometer testing, Car Craft found in 2009 that Mobil 1 0W-30 generated an extra 10 to 15 extra horsepower over conventional 10W-20 and 20W-50 conventional oils, at the cost of some reduced oil pressure. 

Mobil 1 0W-30 generated an extra 10 to 15 extra horsepower over conventional 10W-20 and 20W-50 conventional oils, at the cost of some reduced oil pressure.
Much of that can be attributed to the overall lower viscosity of the tested synthetic, which results in less friction inside the engine than the higher viscosity conventionals. This is one of the advantages of synthetic oil—it can operate effectively at lower viscosities without breaking down. However, unless you’re timing your commute to the tenth of a second, the average driver will never notice the difference.

So what are the benefits of synthetics? Bell Performance, which makes oil additives but not actual synthetic oil, explained in a 2011 article: “Synthetic oils tend to have better high and low-end viscosity performance in very hot and very cold weather. These oils are more resistant to wear and breakdown by oxidation (because they’re engineered to be so) and some synthetic oils can improve fuel economy. They are also more resistant to sludge formation because of this resistance to oxidation and they disperse sludge particles at least as well as regular oil.”

Perhaps the biggest benefit of synthetic oil is almost impossible to observe. Jim Morrissey from Royal Purple told me, “No one really does engine teardowns on a street car to see the wear the way racers do. So it’s really difficult to quantify the improvements you’ll see in terms of engine life and wear from using a synthetic oil.”

While synthetic oil can improve fuel economy, a 2012 Consumer Reports article observed that the small mileage boost (about 2 MPG) occurred mostly right after a cold start, and was offset by the higher cost of the oil. “But what’s behind so many makers of ordinary cars requiring expensive synthetic oil in the first place? SAE Fuels and Lubricants Council chairman James Linden says automakers can save between 0.5 and 1 percent on EPA fuel economy tests compared with 5W-20 motor oil. The tests are run starting with a cold engine, so the lower viscosity reduces friction until the engine warms up. Indeed, when Honda first presented us with details about the 2012 CR-V, company engineers emphasized that they had gained 2 mpg in EPA fuel economy ratings mainly by reducing friction in the engine and other mechanical components, not by introducing new technologies like direct fuel injection or continuously variable transmissions.”

Morrissey pointed out that, “More horsepower equates to better economy if you’re not running throttle wide open.” Royal Purple reports a 1-4 percent increase in horsepower, mainly based on reports from customers and engine builders (Morrissey was unaware of any internal company testing that would confirm those numbers). 

Scheduled oil changes are key

Synthetic oils theoretically let you go longer in between oil changes, which the industry refers to as “drain intervals.” This could result in your buying less oil in the long run, balancing out the added cost of synthetic oil. However, I’d be careful here. The oil filter also plays a major role in determining your drain interval, so if your oil can go 10,000 miles, make sure the filter you use can go the distance as well.

If you have a newer car with an oil use monitoring system, change your oil when it tells you to (you may find yourself going 7,000 or more miles between drains). Monitoring systems track engine temperature, RPM and other factors, measuring how you actually use the engine. They’re considered very reliable. In 2010, Edmunds reported, “One GM car driven by Edmunds went 13,000 miles before the monitoring system indicated the need for an oil change. We sent a sample of that oil to a lab for analysis. The results showed the oil could have safely delivered at least another 2,000 miles of service.”

To go 15,000 miles between oil changes is not something you should be doing. You’re asking for trouble.

By the way, it’s safe to ignore your local oil change joint’s 3,000 mile recommendation. Edmunds also observed, “About the only ones that really need a 3,000-mile oil change are the quick-lube outlets and dealership service departments. In their internal industry communications, they’re frank about how oil changes bring in customers. ‘Many people…know when to have their oil changed but don’t pay that much attention to it,’ said an article in the National Oil and Lube News online newsletter. ‘Take advantage of that by using a window sticker system [and] customers will be making their way back to you in a few short months.'”

Almost all oil manufacturers attach a warranty to their product, guaranteeing that your engine won’t blow up because of a defect in the oil. Some of them require exclusive use of their brand (with the receipts to prove it), while others will warranty your engine within a given number of miles or months from when you put their oil in (again, with receipts as proof). Mobil 1’s warranty covers your engine within 15,000 miles of the oil change or the vehicles OEM recommended change interval, whichever is longer. That these warranties are so generous indicate how consistent and durable modern oils are, and how difficult it would be to prove than an engine failure was not due to a prior defect or other reasons unrelated to the oil.

Other types of oil

Some brands have “extended life” synthetic oils that claim you can go 15,000 miles between oil changes. While there’s nothing wrong with using these oils, I’d still stick with owner’s manual/oil monitoring system recommendations for when to change your oil. I asked Bob Gugino about extended life oils, and his response couldn’t have been clearer: “I think that’s a joke. To go 15,000 miles between oil changes is not something you should be doing. You’re asking for trouble.”

Some oils are marketed as “high mileage” oils, specially formulated for older cars with a lot of miles on the engine. They may use detergents to clear away sludge and chemicals that swell old, dried out seals, theoretically preventing some oil leaks. Paul Weissler wrote about motor oil selection for Popular Mechanics in 2002, and he offered some technical details on what high-mileage oils seek to accomplish. “The higher-mileage oils are formulated with seal conditioners that flow into the pores of the seals to restore their shape and increase their flexibility. In most cases, rubber seals are designed to swell just enough to stop leaks. But the oil refiners pick their ‘reswelling’ ingredients carefully. Valvoline showed us the performance data of one good seal conditioner that swelled most seal materials, but actually reduced swelling of one type that tended to swell excessively from the ingredients found in some other engine oils…These higher-mileage oils also have somewhat higher viscosities. (Even if the numbers on the container don’t indicate it, there’s a fairly wide range for each viscosity rating and the higher-mileage oils sit at the top of each range.) They also may have more viscosity-index improvers in them. The result? They seal piston-to-cylinder clearances better, and won’t squeeze out as readily from the larger engine bearing clearances. They also may have a higher dose of antiwear additives to try to slow the wear process. If you have an older vehicle, all of these features may mean more to you than what you might get from a full synthetic, and at a fraction the price.”

Mechanics I talked to gave them mixed reviews, ranging from, “It’s a great product, I recommend it highly for cars with more than 75,000 miles. It keeps seals lubricated and supple and helps the piston rings stay sealed,” (Bob Gugino) to, “If you change your oil frequently, I see no reason to use high mileage oil,” (Kevin Knox). Ron Hutter said, “Even though I drive a high mileage car, I’ve never used one.” It’s worth noting that the higher viscosity of high-mileage oil means these formulations sometimes have trouble meeting the API rating for fuel efficiency. That means that these oils are the rare type you might find without the API logo on the bottle.

The bottom line here is that oil additives aren’t going to fix leaks. You’ll have to get those old seals replaced eventually. I wouldn’t pay a premium for high mileage oil, but if you have an old, abused engine and can get the oil at a good price, it won’t do any harm.

There are higher end synthetic oils such as Royal Purple, Motul, or Amsoil. They’re often highly touted on automotive forums, but I’ve yet to see anything other than anecdotal evidence that they actually perform significantly better than cheaper oils. They’re usually pretty expensive, but if you find them at a good sale price, they’ll get the job done.

You may see synthetic blend oil—these oils are literally conventional oils mixed with some amount of synthetic oil. They’re cheaper than full synthetics and are offered as a sort of compromise on price and performance. They’re slightly better than conventionals, not quite as good as full synthetics. Some auto enthusiasts even make their own blends, mixing conventionals with full synthetics in some ratio or another. No harm will come from mixing synthetic and conventional oils (or from switching back and forth between them from one oil change to the next). Some manufacturers even use blends for their “factory fill.” This is an option if you’re looking to save a little money—all the major oil makers have their own conventional/synthetic blends.

Which conventional oil?

Full synthetics can cost a lot—three times as much as conventional oils. If you’re looking to save some money, you might consider using conventional oil. As long as your car doesn’t meet any of the criteria mentioned above for using synthetic oil, you can safely use conventional oil. I use conventional oil in my daily driver, a 2001 Toyota Echo with over 150,000 miles on it. If the car was brand new, I’d be using synthetics in it, but it’s been going strong for this long on conventional oil. “I don’t see a big advantage to using a synthetic oil [in a car that’s not high-performance],” Knox told me. “Frequent oil changes are the key. Keep the oil and filter changed regularly and there should be no problem, and you shouldn’t need synthetic oil.”

Which conventional oil is best? Valvoline NextGen performs as well as any conventional oil, costs as little or less, and is made with 50 percent recycled oil. Scientific American reported in 2009 that modern recycled oil is essentially identical to newly refined oil and doesn’t suffer from reduced performance. That added bit of environmental benefit gives NextGen (and other oils made with recycled oil) a slight edge over non-recycled oil. But again, any conventional oil that bears the API logos will get the job done.

Bottom line

Your best bet for motor oil is a synthetic like Mobil 1, Valvoline SynPower, or Castrol Edge, which you can get for a moderate price if you hunt for sales and rebates. If your car and your driving habits don’t demand the extra protection a synthetic oil delivers, you can save money by using a conventional oil. Above all else, follow the oil change schedule in your owner’s manual or as suggested by your car’s oil monitoring system.

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  1. “As we're sure you can understand, ExxonMobil does not discuss formulations publicly, as this information is proprietary.”
  2. “Valvoline SynPower synthetic motor oils are high performing, high-quality oils formulated with full synthetic base oils and top tier additives to provide an increased level of performance. All of Valvoline's SynPower synthetic motor oils are API licensed to ensure quality for North American vehicle application. We have specially designed Valvoline SynPower 5w40 for application in high performance European or diesel passenger cars and this oil carries the specific OEM approvals such as Mercedes Benz, Volkswagen, Porsche and BMW. Our North American SynPower 5w20, 5w30 and 10w30 exceed ILSAC GF-4 requirements and carry the API starburst on the front label. Valvoline SynPower is designed with extra levels of detergent and antioxidant to provide outstanding deposit and heat protection.”
  3. “We generally support any technology that can improve fuel economy. But in this case, we wonder whether some consumers who purchase new cars may feel blindsided by the increased cost of their oil changes. And since 0W-20 mainly only improves fuel economy for the first few seconds of driving, we question whether the fuel economy gains are really worth the added costs for consumers over the life of the car.”
  4. What if You Use the Wrong Stuff?, Consumer Reports, Nov. 2010
  5. Allen, Mark, Synthetic or Mineral Oil? Setting the Record Straight (Finally), Popular Mechanics, Nov. 21, 2007
  6. Biello, David, Can Oil Be Recycled?, Scientific American, August 25, 2009
    “We clean that used oil by using pretty conventional refinery technologies. One of them is vacuum distillation, which dewaters the oil. Used motor oil comes with somewhere between 5 and 7 percent water in it. The first thing you have to do is get the water out of it...Then after that, we go through a hydrotreating process that gets up to 700 degrees Fahrenheit and 1,100 [pounds per square inch]. That infuses hydrogen back into the hydrocarbon molecules and makes it a very high quality re-refined oil.”
  7. Davis, Marlan, Synthetic Versus Conventional Oil, Car Craft, Feb. 2009
  8. Gugino, Bob, phone interview, March 4, 2013.
  9. Hixson, Sean, email interview, March 12, 2013.
  10. Hutter, Ron, phone interview, March 6, 2013.
  11. Knox, Kevin, phone interview, March 5, 2013.
  12. Lampton, Christopher, What do oil additives do for your engine?,, not available
    “Two other common types of engine oil additive are rust inhibitors and detergents/dispersants. The latter help disperse sludge that can build up in the engine over time. Zinc is also added to many motor oils to protect engine surfaces.”
  13. Lentinello, Richard, ‘Rugged’ 1968 Barracuda Logs Nearly 500,000 Miles With AMSOIL, Hemmings Classic Car, Nov. 2010
    “Garner said the car’s quality construction coupled with consistent maintenance have kept the car running smoothly. ‘Not much has gone wrong with the car; it just keeps on running. I just keep after things,’ he said. ‘I change the coolant every year, and every 100,000 miles, I automatically rebuild the carburetor and have a local electric-motor repair shop replace the brushes in the alternator; at the same miles, I replace both the water and fuel pumps to prevent breakdowns. At about 350,000 miles, I replaced the timing chain and performed a valve job. The brake rotors have been in the car for 42 years now, but the rear drums have been changed once and the lower ball joints have been replaced once, too, although I did have to change the clutch three times.’”
  14. Montoya, Ronald, Do I Have To Use the Manufacturer's Oil?,, July 26, 2011
  15. Morrissey, Jim, phone interview, March 12, 2013.
  16. Reed, Philip, email interview, March 20, 2013.
  17. Reed, Philip and Montoya, Ronald, Stop Changing Your Oil,, August 24, 2010
  18. Stark, Ryan, phone interview, March 12, 2013.
  19. Weissler, Paul, How To Pick The Right Motor Oil For Your Car, Popular Mechanics, August 1, 2002

Originally published: May 6, 2013

  • Doug Curley

    I always opt for Castrol Edge, long term trust. I’ve always had great results and it has been recommended to me the most by far.

  • Dana Sands

    I remember reading (maybe in an older issue of Car & Driver) that conventional oil will break down over time while a full synthetic will not. A lot of owner’s manuals will say to change the oil every three months or 3,000 miles (or some other time/mileage interval). Therefore, one of the benefits of using a full synthetic motor oil is that you can ignore the time and only worry about the mileage. Since I work from home and my wife’s job is four miles away, that can be an important benefit for us.

    • Daniel Fleck

      Oil change intervals of 3,000 miles are only recommended by oil change shops. Most manufacturers say 5000, 8000, or even 10,000 now. A lot of newer cars actually have oil life indicators that tell you when the oil needs changed. However, I don’t trust the oil life indicators because they don’t tell you how they make that calculation. I usually forget the mileage and change my oil twice a year (spring and fall) and every other track session (for my fun car).

      • Dana Sands

        You missed the point. The recommended interval in many manuals is OR whichever comes first.

        • Daniel Fleck

          I would say the mileage isn’t as important as the time. Generally if you cover more miles in the same time, most of them are probably highway (easy miles on the oil and drive system) and fewer miles are probably city and repeated starts on the engine (harder on oil). You could probably drive 20k miles on one oil change if they were all highway miles in the summer. OTOH 3000 miles is probably appropriate for repeated short trips in the winter. However, you probably cover 20k highway miles in the same amount of time as 3000 city miles unless you work for UPS or a taxi company.

  • Daniel Fleck

    A slight fix. The number for the oil is weight and viscosity, not two viscosities at cold and hot temps.The weight can give you an idea of cold starting performance but isn’t as critical. If your car is recommended for 5W-20, you would be fine with a 10W-20 or a 0W-20. I would recommend higher weights in the summer (10Ws) and lower in the winter (0W), but really I haven’t noticed much of a difference in weights. They usually advertise the 0W oils as more fuel efficient, but we are talking maybe 1/2% at best potential increase in fuel economy. Immeasurable except in a lab.

  • Ben

    This was an excellent, well researched article. Thanks for doing it.

  • David

    Exxon-Mobile refuses to add sexual orientation to its official equal employment opportunity statement, so I refuse to purchase any of their products. I realize that your classification of “Best” doesn’t take corporate policies into effect, but for me the 2nd place products are plenty good enough!

    • usernameguy

      ExxonMobil just announced they are extending benefits to same-sex couples starting October 1. I will continue my policy of buying whatever’s on sale that day.

  • Twelve of Five

    6,000 words to say that it really doesn’t matter what kind of motor oil you use as long as you follow the instructions in the owner’s manual?

    I appreciate geeky thoroughness as much as the next guy, but this might be an oil filter too far.

    • C2H5OH53

      The article is hogwash! The problems created by the incorrect selection of motor oil are very common in modern engines. This article completely ignores that fact. Virtually every manufacturers has faced oil related engine damage and had to resort to specialized oil service ratings. Chrysler, Toyota, Mercedes, BMW, VW/Audi have all had highly publicized lawsuits over these issues.

      The pertinent oil service ratings that technicians and car owners must recognize in order to select the appropriate oil for a given car (In North America) includes but is not limited to:
      VW 502, 503.01, 504, 505, 505.01, 507
      MB 229.1, 229.3, 229.31, 229.5, 229.51
      BMW LL-98, LL-01, LL-04
      GM 6094M, 4718M, LL-A-25, LL-B-25, dexos1, dexos2
      Chrysler MS 6395 (Numerous versions)
      Ford WSS-M2C945-A, WSS-M2C946-A, WSS-M2C931-B, WSS-M2C913-A/B/C
      Honda HTO-06
      ACEA A1/B1, A3/B3, A3/B4, C1, C2, C3, C4
      API approval is insufficient for any car sold in America
      ILSAC GF-5 approval is still appropriate for SOME Japanese ans Korean cars

      The dynamic viscosity is critical for high shear wear protection.

      The kinematic viscosity is critical for the proper operation of hydraulic devices such as VVT cam phasers and also for proper piston and ring cooling.

      The SAPS level is critical for maximum oxygen sensor and catalyst life.

      Selecting oil based on brand is kinda stupid. every oil company makes numerous different versions of each “Full synthetic 5W-30″ with different SAPS levels, different dynamic viscosity (5W-30 does NOT limit the dynamic viscosity) , different base stocks, etc. So brand based selection is useless

  • RonV42

    I’ve been using Amsoil for 15 years now and have been following their extended oil change guidelines. My SAAB 9-3 SE, before I sold it, had over 185,000 miles on it and I would change the oil twice a year. Our 2001 Prius had 160,000 miles on it before we donated it to charity and would do the annual oil change with filters at 6 month intervals. My current Honda CR-V has over 80,000 miles and still going strong after 6 years and annual oil changes.

    I have had oil analysis come back with clean bills of health on every car I have run synthetics and following the extended oil change regiment. I don’t know where the fear comes from. It may the 3K/3 Month syndrome you hear all the time when you take your car into the dealer. I get this from Honda, I take the CR-V in when the maintenance minder comes on to do the tire and other maintenance but tell them to skip the oil change. Every time they come out with a dealer prepared sheet of recommended services that are never in the owners manual and of course the 3K/3 Month oil change is always listed.

    All I can recommend is that folks follow their owners manual and real testing by oil analysis services as a guideline for oil changes.

  • vivekgani

    You may want to google for the numerous stories of subaru turbo engines being ruined from using mobil 1 synth and waiting until 7k for oil changes. There’s something about the turbo subaru engine where the oil tends to lose viscosity faster.

    • drnimrod

      It’s actually not just limited to Subaru engines. Pretty much everyone I know who uses Mobile One has to change their oil after roughly 3500 miles. Any mileage after that and engines start to knock.

  • Andrew Hammond

    I personally have had to replace the engine on my 2006 Subaru WRX STi. I had a cam shaft seize from low oil just shy of three months (and a long way shy of 3k) from having the oil changed using Mobil 1. I’ve spoken with three different mechanics about it and they all agree that Mobil 1 has a nasty habit of getting eaten up by the temperature differentials in big to medium turbo engines. I’m currently using Shell Rotella T6 at the recommendation of those same three mechanics (although they did recommend Motul, if I wanted to spend a lot of money). I also learned the painful lesson of checking my oil every time I fuel up.

    • tony kaye

      An STi is not an average car :(

      • Andrew Hammond

        Sure, however turbos are starting to get pretty common.

        • C2H5OH53

          For engines that require a low dynamic viscosity (most Asian and American models, NOT Euro models) the Honda HTO-06 service rating combined with ACEA A5/B5 approval and GM dexos1 licensing will deliver what you need. The combination of all three ratings is hard to find but worthwhile. The Honda HTO-06 specifically addresses the needs of turbochargers in low dynamic viscosity applications.

    • C2H5OH53

      You simply used the wrong Mobil 1. Mobil makes a wide range of Mobil 1 products. Depending on your driving conditions you may require a higher dynamic viscosity (still the same SAE viscosity rating) than the typical Mobil 1 (or any similar brand). That Rotella T-6 has the correct dynamic (HTHS) viscosity (over 3.5 cP @15C) but is formulated for diesel applications, and is the wrong kinematic viscosity (which could lead to insufficient ring cooling, ring sticking, microwelding, etc). And, that’s still probably not the whole story. Be very careful of the WRX STI advice you get on Suby forums. the American Market engines are clearanced very differently than the Japanese market engines and other Market WRX STI. They won’t live well on the same oil.

  • ctchrisf
    • tony kaye

      Here is what we had to say about them

      “Which conventional oil is best? Valvoline NextGen performs as well as any conventional oil, costs as little or less, and is made with 50 percent recycled oil. Scientific American reported in 2009 that modern recycled oil is essentially identical to newly refined oil and doesn’t suffer from reduced performance. That added bit of environmental benefit gives NextGen (and other oils made with recycled oil) a slight edge over non-recycled oil. But again, any conventional oil that bears the API logos will get the job done.”

      • C2H5OH53

        API SN approval fails to meet the minimum requirements of every car sold in America! ILSAC GF-5 fails the minimum standards of all but most Japanese and Korean cars (fails GM, Ford and Chrysler)There is nothing wrong with recycled as long as it meets the appropriate industry standards. But, Valvoline NextGen fails important requirements for many modern cars. It fails Honda HTO-06, dexos1, dexos2, ACEA A1/B1, A5/B5, Chrysler MS 6395 (the CURRENT version), etc, etc. It also fails VW 502, 503.01, 505, 505.01, MB 229.1, 229.3, 229.5, 229.31, 229.51, BMW LL-98, LL-01, LL-04

  • Me

    Excellent article — thank you … this should be republished on every diesel truck forum out there …

  • Soyntgo4it

    Mobil one sucks my car loves to burn it, but when I use another its doesn’t burn any oil.

    • tony kaye

      What type of car do you drive? If you don’t mind me asking

      • Soyntgo4it

        Honda product.

    • Soyntgo4it

      So I use Royal Purple no issues with that so sticking with it now. Wont switch back now.

      • C2H5OH53

        Some of The Royal Purple line was (still is I assume) repackaged Mobil 1. Sooooooooooooooooo……………………

        • Dusk Falls Castle

          it is but royal purple is essentially Mobile 1 with some additives to help keep the engine clean. as well as additives for o-rings, gasket health. (Keeps them from drying out or breaking down so much) Basically what you are paying for in Royal purple is Mobile 1 shampoo with conditioner! HAHA! Same performance, a little better on the buildup and gasket, o-ring. But regular maintenance with Mobile 1 will do the same thing really.. *shrug* but ROYAL PURPLE IS PURPLE!!! SO all in what you want to pay for rofl!

  • drnimrod

    Mobile One burns burns burns. This review has pretty much tossed your credibility out the window.

  • C2H5OH53

    You didn’t mention the numerous ACEA oil service ratings that are all much more stringent than API or ILSAC and can be used to identify the differences that your articles suggests don’t exist.

    • tony kaye

      The research on this guide is solid & a more stringent set of standards isn’t going to make a difference. – via our expert.

      • C2H5OH53

        Who is your “expert”? What are his credentials? You list a significant number of journalists and hobbyists, but I don’t see any “experts” credited. And your article describes a supplement blender as an additive manufacturer! (Huge Red Flag). And then you apparently assume that the SAE viscosity rating is an accurate indication of the HTHS Dynamic viscosity (even bigger red Flag). Car Craft was one of the Hobby magazines that sold the false perceptions about Zin Phosphates while stumbling over some pretty obvious dynamic viscosity issues (addressed 20 years earlier by ACEA) Exxon/Mobil (and their associates at Infineum) does a great job and is often my choice. But, it’s incredibly misleading to recommend any brand over OEM and ACEA standardized service ratings. If you are going to “research”, do it with someone who has valid credentials. You could have gotten this quality of “solid research” from any unlicensed mechanic.

  • flipped4geekstuff

    I love Mobil 1. I use High Mileage M1 5W20 summers and 0W20 winters in my 2003 Honda Civic. I rarely have to top off the oil. I recently had an oil analysis done after where the I went 9223 miles before changing the oil and filter. They love the results and recommend I can go as long as 11,000 miles before my next change. I won’t go that far since I change the oil and filter every six months. It’s good to know though that Mobil 1 is so durable! I also use the basic Purolator filter and it does great keeping the oil clean.

  • Dave

    All synthetic oils exceed o.e.m. specifications…

  • Ratna Kusumawardani

    Wow…this motor review is good. the best i ever read. i like it


  • Charles Edward Ross IV

    Couldn’t agree more, I think anything above Mobil One as far as price goes is just a gimmick. I’ve been using Mobil One for years.

  • Tien H

    I’ve been using mobile one and it’s great, however I’m strongly considering SynBlend due to cost.

  • Kirk Masters

    Mobil 1 has long been the synthetic oil of choice. A 20% blend provides an almost equivalent amount of protection. Mobil 1 sticks to the engine parts to prevent dry start. That is sooo important in our C-Max hydrid as it stops and starts so often. It also has built in viscosity adjustment and a higher temperature limitation for less oil burning. Many supplies license it and sell it under their name. Castrol hated to pay these royalties and make their own which in reality is not synthetic but they were allowed to call it that. For that reason, I will not buy Castrol Synthetic as it isn’t. We just got our used C-Max in the fall and the oil still looks clean in the spring. As for oil filters, Napa Gold is considered to be one of the best ones out there. Fram was sold the guts removed and replaced with cheaper parts so it is no longer recommended. That is what one review found out when he cut open the various oil filters. My old Engineering Prof who was an expert on lubrication and taught the advanced course recommends synthetic oil for reasons that I have stated. The most important thing about oil is getting to the part ASAP

  • Austin

    Hey, Maybe you could write a follow-up article? I’ve seen a new oil called “Magnatec” by Castrol. It says on the bottle that it holds on to engine parts more than other oils while the car is off, However it doesn’t come as a 5w30 Full Synthetic – yet, at least; that viscosity is available in Synthetic, though. I haven’t tried it yet, it does sound good in theory.

  • Austin

    Speaking for Mobil-1 here:

    On a 2000 Caravan 3-Litre with 148.8xx miles on it, I changed the oil to Mobil-1’s High Mileage Full Synthetic 5w30 and installed a Bosch filter on it. About 1800 miles later the oil still comes out looking clear.

    On a 1999 Diesel Suburban, I had the oil switched to Mobil-1’s Full Synthetic Heavy-Duty Turbo Diesel Oil and got a Mobil-1 filter on it too. The oil still came out looking clear even 200 miles later, on a Diesel. Now, I’ve heard that I shouldn’t be surprised if oil comes out dirty immediately after the oil change when it comes to Diesels all due to soot – but it wasn’t so with this. I haven’t had enough miles on it to change the oil yet, though – I’ll go with 5k mile changes on it.

  • Austin

    On an old 1980s Chevy with a 5.0 Litre Gas engine, I had (ignorantly) abused it by putting some 5w20 in it (Supertech, Full Synthetic) and running it on that. As you may possibly imagine, that caused the engine to run louder than it would have if I used the proper 30 weight. I didn’t run the car on it for a lot of miles though as I rarely used it, but when I switched back to a 30w oil (Pennzoil High Mileage, Conventional, 5w30) that got it to run quieter. I also added some STP Oil Treatment which made it run even quieter, but it also thickened the oil – Which may not be bad given the engine’s age.