Bustin’ Myths About Synthetic Lubes

Courtesy of AMSOIL

Many people with questions about synthetics haven’t known where to turn for correct information. Is it super oil or snake oil? Some enthusiasts will swear that synthetics are capable of raising your specialty car from the dead. On the other hand, the next fellow asserts that synthetics will send your beloved car to an early grave. Where’s the truth in all this?

In an effort to set the record straight, here we’ve assembled 10 of the more persistent myths about synthetic motor oils to see how they stack up against the facts.

Synthetic motor oils damage seals.


It would be foolhardy for lubricant manufacturers to build a product that is incompatible with seals. The composition of seals presents problems that both petroleum oils and synthetics must overcome. Made from elastomers, seals are inherently difficult to standardize. Ultimately it is the additive mix in oil that counts. Additives to control seal swell, shrinkage and hardening are required, be it a synthetic or petroleum product.

Synthetics cause engines to use more oil.


Synthetic motor oils are intended for use in mechanically sound engines, that is, engines that don’t leak. In such engines, oil consumption will actually be reduced. First, because of the lower volatility of synlubes; second, because of the better sealing characteristics between piston rings and cylinder walls, and finally, because of the superior oxidation stability (i.e. resistance of synthetics against reacting with oxygen at high temperatures).

Synthetic lubricants are not compatible with petroleum.


The synthesized hydrocarbons, polyalphaolefins, diesters and other materials that form the base stocks of high-quality name-brand synthetics are fully compatible with petroleum oils. In the old days, some companies used untested ingredients that were not compatible, causing quality synlubes to suffer a bum rap. Fortunately, those days are long gone. Compatibility is something to keep in mind, however. Whether using petroleum oils or synthetics, it is usually best to use the same oil for topping off that you have been running in the engine. That is, it is preferable not to mix your oils, even if it is Valvoline or Quaker State you are using. The reason is this: the functions of additives blended for specific characteristics can be offset when oils with different additive packages are put together. For optimal performance, it is better to use the same oil throughout.

Synthetics can’t be used with catalytic converters or oxygen sensors.


There is no difference between synthetic and petroleum oils in regard to these components. Both synthetic and petroleum motor oils are similar compounds and neither is damaging to catalytic converters or oxygen sensors.

Synthetics void warranties.


No major manufacturer of automobiles specifically bans the use of synthetic lubricants. In fact, increasing numbers of high-performance cars are arriving on showroom floors with synthetic motor oils as factory fill. New vehicle warranties are based upon the use of oils meeting specific API Service Classifications (for example, SG/CE). Synthetic lubricants which meet current API Service requirements are perfectly suited for use in any vehicle without affecting a new car warranty. In the 25 years that AMSOIL Synthetic Lubricants have been used in extended service situations, and over billions of miles of actual driving, these oils have not been faulted once for voiding an automaker’s warranty.

Synthetics last forever.


Although some experts feel that synthetic base stocks can be used forever, it is well known that eventually the additives will falter and cause the oil to require changing. Moisture, fuel dilution and acids (the by-products of combustion) tend to use up additives in oil, allowing degradation to occur. However, by “topping off,” additives can be replenished. Through good filtration and periodic oil analysis, synthetic engine oils protect an engine for lengths of time far beyond the capability of non-synthetics.


Since their inception, manufacturers of synthetic motor oils have sought to educate the public about the facts regarding synthetics, and the need for consumers to make their lubrication purchasing decisions based on quality rather than price. As was the case with microwave ovens or electric lights, a highly technological improvement must often overcome a fair amount of public skepticism and consumer inertia before it is embraced by the general public.

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