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Separating Facts from Friction

Motor Oil

You’ve seen those slick ads for motor oils, but after you get beyond basic protection, the claims get slippery, because oil-makers don’t supply independent test results to back up their boasts. And some industry seals of approval don’t carry a lot of weight. 

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Commercials from the makers of motor oil that boast that their product does the best job of protecting your car’s engine are standard fare. So are ads that fling charges against rival oils, such as the Castrol Edge spots that claim that the motor oil provides eight times better wear protection than Mobil’s does. Common to all of the ads, it seems, are warnings that your vehicle’s engine is at risk from friction, sludge, varnish and wear from motor oil than can be contaminated, oxidized, cooked or otherwise broken down.

The fact is that virtually every motor oil that is sold these days will deliver ample protection for the types of automobiles that most of us drive—provided, of course, that the oil is changed on schedule and that the oil meets the automaker’s engine requirements.

Unfortunately, the differences between the motor oil brands increasingly are blurred, and manufacturers are secretive about their testing. This means that you get—at best—a blend of hype and facts.

SYNTHETIC CLAIMS. Although there used to be strict government standards regarding what motor oil qualified as a synthetic oil, those definitions no longer apply. Oil-makers increased the processing of their oil, and the federal government responded by expanding its definition of what qualifies as a synthetic. The murkiness of government standards and the lack of third-party testing has resulted in a war of words among competitors. (Even though industry insiders might debate just how refined oil must be to qualify as a synthetic, you should know that synthetic oils all deliver comparable performance.)

It’s enough to make your head—if not your wheels—spin.

“I tell people that ninety-five percent of the words on a can of engine oil are marketing hype,” says James Garthe, who is an agricultural engineer at Penn State University and has conducted motor-oil research for the school. “Don’t believe all that crap that’s on there.” For instance, he says, an oil might boast of its anti-sludge properties, but “all [motor oils] have some anti-sludge additives.”

So, what you get when you buy into a major brand’s claims is a big dose of marketing. For instance, Walmart’s house brand of synthetic oil passes the stringent “Corvette” standard that General Motors has set for motor oils. (We’ll have more on that later.) It’s refined by a major oil-maker. The only thing that Walmart’s motor oil is lacking is the colorful branding and the flashy TV commercials.

After all, the raw material for synthetic motor oils and synthetic motor oil blends is still conventional mineral oil. About 5 percent of the crude oil that is pumped from the ground is suitable for making motor oil; that’s what’s called the base stock—the base oil that comprises most of each quart that you buy. Whether it’s marketed as conventional, synthetic or a blend, motor oil typically falls into four different categories—Groups 1 through 4—says Thom Smith of oil-maker Ashland Valvoline. The higher the group number is, the greater the amount of processing that’s been done to the oil (to make the oil’s molecules behave more predictably)—and the more expensive that the oil is.

Synthetic doesn’t have a lot of meaning anymore,” concedes Matthew Snider of GM. “A variety of products can be legally marketed as synthetics.” All that the term synthetic means is that Federal Trade Commission deems that the oil has been sufficiently processed and modified to qualify as “synthetic.”   

What you need to know about synthetic motor oil is that it’s widely accepted that any motor oil that is classified as a synthetic delivers better protection than conventional oil does against thermal breakdown—the tendency of the oil to deteriorate (and thus not lubricate as well) when it’s heated. It also curtails wear, increases resistance to contamination, provides better flow at cold temperatures, and reduces sludge and deposits on piston rings. In other words, even though you’ll pay more—typically $1.50 to $3 per quart—for a synthetic motor oil than you would for a conventional motor oil, you’ll get more in return. 

ADDING IT UP. Generally speaking, a synthetic motor oil is considered to be one that includes a variety of additives to distinguish it from a conventional oil. (However, even the lowest price conventional oils include a few additives.) The additives that oil companies mix with their base oil will determine its performance. For instance, conditioners that help to keep seals flexible and reduce oil leaks are typical of additives in motor oils that are marketed to drivers of high-mileage cars. But they won’t necessarily help if you’re looking to guard against engine wear.

Lubricants are formulated to address dozens of properties, says Bob Sutherland, who is the principal scientist for Shell Oil’s Pennzoil brand, but oils that try to cover all the bases cost more. (Motor oils that perform well in virtually all conditions tend to cost $9 to $10 a quart—compared with as little as $2 a quart for the most basic of conventional oil and $5.50 for the least expensive synthetic.) “Unless you are at the very high echelon,” Sutherland says, “you can’t be all things to all people.”  

PINNING IT DOWN. Your engine’s specifications, not any oil-maker’s claims, are what should determine your choice of motor oil.

PINNING IT DOWN. Your engine’s specifications, not any oil-maker’s claims, are what should determine your choice of motor oil.


Because of their price, these all-purpose oils sell in low volumes, and no mainstream oil-maker makes them. Obviously, there’s nothing that prevents manufacturers from charging a lot for bad oil, but industry experts say it’s not possible to do the opposite—make the best oil cheaply. Without third-party testing, of course, there’s no way to compare.

So, why not just buy a low-price conventional oil that has fewer additives and use an aftermarket product to address a specific engine issue, such as stopping leaks?  Motor oil-makers, naturally, point to their formulations for anti-leak motor oils and say additives aren’t needed for typical car engines.

But David Kargas of engine-oil additive-maker STP argues that “Motor oils are formulated with the minimum level of additives required to pass the tests.” Consequently, he says, an aftermarket product that would boost the level of anti-wear additives would result in better engine performance.  

Oil-makers dispute the “more is better” claim regarding additives, and American Petroleum Institute (API), perhaps unsurprisingly, comes down on the side of oil-makers. The trade association represents the oil and natural-gas industry, which includes producers, refiners, pipeline operators and tanker operators. It also sets industry standards and tests some motor oils to check that they meet those standards. API says it tests oils only in their unadulterated form and is not in position to evaluate additives. Although that explanation sounds weak, automakers with which we spoke say aftermarket additives are unnecessary and could be potentially detrimental to the oil.

But based on our research, we believe that oil additives that target specific problems, such as leaks or oil burning in high-mileage engines, could be beneficial—if you chose a budget-price conventional oil, rather than a synthetic oil that already contains the additives that alleviate those problems.  

TESTING, TESTING. You don’t want to earn a doctorate in chemistry; you just want to pick a motor oil that will ensure that your engine doesn’t lock up and leave you stranded. So, can’t you just look at some neutral, unbiased test score and pick the oil that has the best result? Unfortunately, no.

“I wish there were a chart that showed in a simple fashion which is the best oil,” says Kevin Ferrick of API, “but unfortunately we don’t do that.”

Don’t hold your breath waiting for an independent test that determines which oil is the best, Garthe says. “That costs a zillion dollars to do it, so it doesn’t get done.” Motor oil-makers perform such tests themselves, he says, but most aren’t interested in sharing the information besides, of course, that their oil came out on top.

One company that did share its test results with us is Amsoil, which makes a specialty high-performance synthetic oil that costs about $9 per quart—compared with about $5.50 per quart for the big national brands’ synthetic oils. You shouldn’t be surprised to learn that Amsoil’s tests show that its oil tops all of the mainstream brands. What was notable was that other brands took turns in second place—the brand depending on which engine issue was the focus of the test. Although that’s a far cry from independent testing, Amsoil has no vested interest that we know of in the finishing order of the other brands that were tested. The results support what industry experts tell us about the mainstream brands that tout specific purposes—some are better than others at specific tasks, but it all depends on which task that you choose. 

STANDARD RESPONSE. So, how should you pick a motor oil? It should go without saying that before you do anything else you should check your vehicle owner’s manual to see which type of oil is recommended by the manufacturer, both in terms of certifications (the seals of approval from industry groups and automakers that show that the oil has passed various performance tests) and viscosity. As long as your oil choice meets your engine’s specs, brands are inconsequential. Sadly, the various certifications are of somewhat dubious value in and of themselves.

The most common baseline certification is API’s seal. But don’t give it much credence when it comes to picking an oil: Even API admits that its seal certifies only a minimum performance rating that is met by virtually every motor oil that is sold. API says that this year it will update its seal to SN standards, which will mean a boost to its anti-sludge requirements from the current SM. However, that doesn’t mean that fewer oils will qualify for certification. API tweaks its specs every few years, and the oil-makers easily can adjust their formulas to meet the new requirements. You should be aware that newer certifications supersede older ones, so if your older car requires SJ or SL motor oil, the current SM and the upcoming SN oils will work just as well.   

You’ll notice that some motor oils list certifications that come from other organizations, too, but because no one tracks what percentage of oils achieves any agency’s standard, we wonder whether  these certifications are any more helpful than API’s in evaluating which oil to buy. There’s International Lubricant Standardization and Approval Committee (ILSAC), which comprises Japanese and U.S. automakers. ILSAC also is considering a change in its current standard to include more-strict anti-sludge requirements. European automobile manufacturers’ Association des Constructeurs Européens d’Automobiles (ACEA) 2008 certification might indicate better protection in specific areas—ACEA’s standard has tougher limits than the API standard on sludge formation, for instance.  

Most automobile manufacturers have their own testing requirements for motor oil, too, but you should know that just because an automaker uses and recommends a particular brand of oil doesn’t necessarily mean that that brand is better.  For instance, Mobil 1 is endorsed for GM and Mercedes models, and Castrol boasts that it is the factory-fill oil for BMW and Volvo. Although it’s obvious that no amount of money would get an automaker to recommend a bad motor oil (jeopardizing its vehicles), what isn’t known is whether oil-makers pay for the endorsement.

But all automakers concede that as long as an oil meets the requirements for viscosity and test certifications that are cited in the owners manual, they are happy with any brand of oil that you use. You should be aware that most of the test standards are similar, so an oil that boasts that it meets, say, five manufacturers’ standards, is really just a mild endorsement and likely doesn’t indicate notably better performance than what you’d get from another oil.  

Still, some automakers feel the need to establish more-rigorous specifications. GM has two specifications—one for its mainstream models and another for its high-performance Cadillac and Chevrolet Corvette models. The GM6094M mainstream specification is similar to ILSAC’s, but it also requires that engine seals won’t leak and that oil flows at low temperatures. For the extreme requirements of high-performance engines, the company developed the GM4781M specification (the so-called Corvette/Cadillac standard).

This standard has higher benchmarks than GM6094M does for piston cleanliness (no carbon gunk stuck to the piston), high-temperature oil oxidation (when the oil is burned and loses its lubrication properties) and viscosity stability (the ability of the oil to not become too thick when it’s cold or too runny and thin when it’s hot).

This standard seems to mean something. Although most major oil-makers have a formulation that qualifies, you should know that GM’s list from this past June showed that there were only 16 approved formulations out of the hundreds that are sold in the United States.

Although there seems to be a clear demarcation in motor oils that pass this standard when compared with the other certifications, Snider says it’s a waste of money to use costlier motor oil that meets GM’s tougher requirements in vehicles that don’t require it. “The best” is an inappropriate term, he says. “The best oil is that which the vehicle was designed to run on.”

By using budget-price generic house brands or private-label conventional oil, you can, of course, save some money, but that’s only if those cheaper alternatives have the same certifications that are required for your car’s engine. We found that most do.

SLIDING AHEAD. With so much emphasis being put on the marketing of “green” this and “green” that, we’re not surprised that the motor oil segment is getting eco-friendly, too. And you’ll notice that a few manufacturers now urge you to scratch your eco-itch with recycled oil or an oil that is made of biological sources that aren’t petroleum-based.

The performance of recycled oil from Safety-Kleen compares with that of conventional mineral oils, the company says, because the used oil is refined by a similar process as the crude oil that is the source of regular motor oils, and, just like those oils, it meets API certification. And recycled oil typically costs about the same as conventional oils do.

But renewable oils that come from vegetable oil or recovered animal fat—also known as bio-oils—have a tougher time meeting the various certification standards than conventional oils do. At press time, only G-Oil from Green Earth Technologies achieved API SM certification. Does that reflect a pro-petroleum bias? It would appear not. API says it only sets the test requirements and leaves it up to manufacturers to provide the test results that show whether its products pass or fail. So, the burden of proof falls on the companies that make such oils to convince API, as well as us, of their performance. As long as green products fail to achieve even API’s minimal SM standard, they likely will cater only to the ecologically minded set.

Of potentially larger significance might be something small. Motor oils that involve nanolubricants, which aim to reduce friction and boost engine efficiency through the use of nanosize carbon particles that act as microscopic ball bearings between an engine’s metal surfaces, might be around the corner. Developers tout a significant improvement in oil lubricity—its slipperiness—by adding just 1 percent nanolubricant to motor oil, and that could translate into less friction between engine parts.

The resulting lower levels of heat and wear means that those parts won’t wear down as quickly. But don’t expect to see such a product on store shelves any time soon. All of the oil companies with which we spoke say they are investigating the technology, but none would say when—or if—such a product might be rolled out or at what price.    

And “if” might be the correct outlook for nanolubricants, given the cautionary precedent of PTFE Teflon. PTFE Teflon was ballyhooed in the 1980s as the next great leap forward for motor oils. But it never was incorporated into mainstream products, and DuPont concluded at the time that it wasn’t suitable for such use. Besides, nanolubricants, like all nanomaterials, raise concerns with several agencies about their impact on your health because of their tiny size and their ability to collect everywhere—including in our bodies. And no one wants his/her motor oil to change anything except how his/her engine performs.  

Dan Carney is an automotive journalist who covers the industry for MSNBC.com and Popular Mechanics magazine. He has covered automobiles for 20 years.

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