Ten or 15 years ago, choosing the oil for your car was simple. All you needed to know was the viscosity — 5W-30, for example — and you could get a few bottles at the local auto parts store. But this simplicity is starting to go away.

General Motors' transition to a new oil specification for all its 2011 and newer vehicles is bringing new attention to the issue of manufacturer oil specifications. GM isn't the first to require such a specification, but its move signals a change in the car-maintenance landscape.

A manufacturer's oil specification is a unique blend that an automaker creates and mandates for use in its vehicles. GM's new oil product, Dexos, consolidates its five prior recommended oil specifications into two blends: Dexos1 for gasoline-powered vehicles and Dexos2 for diesels.

GM and other automakers warn that failure to use their factory-specified oils could void a car's warranty. These new oil specifications can also create confusion and cost issues for consumers who change the oil themselves or take their cars to local mechanics who may not be aware of the changes.

Oil Has Changed
The oil inside a modern engine might look just like it did a decade ago, but it actually is far more advanced. The American Petroleum Institute (API) and the International Lubricants Standardization and Approval Committee (ILSAC) have set the standards for oil for the past 60 years and have changed the specifications roughly every five years. Oil needs to change to meet increasing emissions regulations, offer better protection against sludge and improve fuel economy.

"There has been a significant increase in lubricant quality in the past 20 years," says Robert Sutherland, principal scientist for Pennzoil passenger-car engine lubricants. "But there has also been a significant increase in the stress that the engines put on the lubricant."

Sutherland says it's a game of leapfrog. As the hardware moves forward, the oil specifications must also change to handle the additional heat and properly lubricate the engine. He adds that the tolerances in a modern engine are closer and tighter, which means that the oil's ability to keep critical engine parts clean is more important than it used to be.

Automakers' Own Recipes
The API and ILSAC standards are the baseline, says Timothy Miranda, senior engineer for race oil and field testing for Castrol Lubricants, which manufactures oil for automakers such as Audi, BMW and Volkswagen. Automakers are free to improve upon the standards as long as they meet the minimum requirements.

"They may choose to have their own specifications because of a unique aspect of their engine design," Miranda says. For example, if a car is turbocharged, it might require synthetic oil rather than conventional oil.

This manufacturer standard is more common among the German automakers, thanks to more stringent European oil specifications, Miranda says. Rather than have numerous blends for different regions, each automaker created one specification for its vehicles. They have brought those standards to the U.S., as Audi, BMW, Mercedes-Benz and Volkswagen all have their own oil formulations.

According to Miranda, most American and Japanese automakers have tended to stick with the API guidelines. This means that they recommend any oil with the API "starburst" or "donut" symbol on its label.

GM distanced itself from the API guidelines with the introduction of Dexos. According to GM, the Dexos oil specification will decrease harmful piston deposits by up to 28 percent and improve fuel efficiency by up to 0.3 percent compared to the older ILSAC GF-4 specifications.

GM licenses the Dexos certification to motor oil manufacturers that can then choose to offer a full-synthetic variation, as long as it meets the requirements. Since Dexos-certified oil is compatible with older cars, the specification will also affect owners of pre-2011 GM vehicles who get their cars serviced at dealerships. Though Dexos isn't being mandated retroactively, chances are dealers will fill their bulk tanks with it to consolidate their oil inventory.

What This Means for the Consumer
More expensive maintenance: "The OEMs are looking for protection and the customer wants longevity," Miranda says. This protection comes at a cost. As manufacturer oil specifications become more common, the auto industry moves farther away from conventional oil and toward synthetic blends or fully synthetic oil. While these newer oils offer better protection and longer intervals between oil changes, they also have a higher price tag.

This price bump can be offset by the automakers who offer free maintenance programs. But when the coverage runs out, a customer who is not used to paying for a synthetic oil change could experience some sticker shock when faced with a $90 oil change.

Potential warranty problems: The language in some owner's manuals suggests that using an oil other than the one specified by the manufacturer will void the car's warranty. This is not the case, says Thom Smith, Valvoline's vice president of branded lubricant technology.

According to the Magnusson-Moss Warranty Act, the onus would be on GM or another automaker to prove that a non-manufacturer oil damaged the engine. If dealers deny the warranty claim without first investigating it, they are in violation of the act, Smith says.

Consumers just need to make sure that any alternate oil they use is comparable in quality to the automaker's specified oil. Many oil manufacturers, including Valvoline, are so confident of their product that they offer their own warranty against engine damage that their products might be alleged to have caused.

If talk of voided warranties and engine damage makes you nervous, just use the manufacturer's specified oil for the duration of the warranty. Keep in mind that a vehicle's engine falls under the drivetrain warranty (also known as the powertrain warranty). In most cases, this is longer than the traditional bumper-to-bumper warranty.

Your local mechanic or quick-lube facility may not be aware of your car's specific oil requirements. You can still go to these places, but be sure to ask ahead of time what kind of oil they will use. Or bring your own oil to avoid any confusion.

Required manual reading: Not all cars require a manufacturer-specified oil. They do have a recommended viscosity, such as 0W-20, however. Check the owner's manual for any mention of a required brand or specification. If the manual doesn't name one, you can save money by buying oil at an auto parts store. Make sure it's the correct viscosity.

There are money-saving opportunities to be had even if your vehicle does call for a manufacturer-specified oil. For example, GM has a Web site that lists the approved Dexos oil manufacturers. Most of their products are available online or at auto parts stores and may cost less than at the dealership.

In some situations, the manufacturer-specified oil may not be in stores or it might cost more than you want to spend. Your vehicle's owner's manual will usually list the specifications for an equivalent oil that meets the automaker's standard. Does that mean it's just as good as a manufacturer-specified oil such as Dexos? There's controversy on this point.

Flack from the oil wars: Tom Read, a spokesperson for GM's powertrain technology group, warns that using an alternative oil might diminish performance.

"If a customer uses a non-licensed engine oil that is simply ILSAC GF-5 quality, they will not enjoy the benefits of using a Dexos-licensed product," Read says. Those benefits could include better low-temperature performance, cleaner pistons and better aeration performance, he says. "This could be especially important as the engine oil ages."

Read's case for Dexos sounds compelling, but Valvoline's Smith isn't buying it.

"Our SynPower 5W-20, 5W-30 and DuraBlend 5W-30 went through all the Dexos testing and passed all the requirements," Smith says. "But we felt that carrying the Dexos name was not providing the consumer with any value."

Rather than raise the price of its oil to offset the cost of licensing the Dexos name, Valvoline chose to forgo the license and keep the prices lower, he says.

Smith says that GM's engine-performance warnings are part of its goal to drive consumers to dealerships for their maintenance. "We feel that they are taking choice away from the consumer," he says.

Focus on the Oil Basics
Setting aside the claims and counter-claims of manufacturer-specified oil superiority, here's all you have to remember: As long as you follow the oil specifications shown in your owner's manual, you have nothing to worry about.

In the event that the dealership tries to void your warranty over the use of non-manufacturer oil, know that the Magnuson-Moss Warranty Act will protect you. If your vehicle doesn't have an oil specification, you have more flexibility in choosing your product. Finally, make sure you know the proper viscosity for your car and change the oil at the proper interval.

Use only 5W-20 engine oil, meeting
specification WSS M2C925-A