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Synthetic Oil Myths

March 5, 2021

Synthetic motor oil has been a hot topic for quite a while, and it is not going away anytime soon – especially since many auto manufacturers are moving toward synthetic oil in their engines straight from the factory. Synthetics offer several advantages over conventional motor oil. But, just like tales of Bigfoot, the Loch Ness monster, or the need for an oil change every three thousand miles, synthetic oil myths linger on.

Here are a few of those myths.

Synthetic motor oil is not real oil

Some skeptics view synthetic oil as “fake” oil – something not natural. But that is not the case. Sure, synthetic oil is created artificially in a lab, but the term “synthetic” refers to the process, not so much the material. While different base oil stocks may be used in the process (from one product to the next), most synthetic motor oils begin their lives as a highly-refined base oil derived from petroleum. What sets a synthetic apart is its uniformity at a molecular level, its freedom from impurities, and its ability to contain high-quality additives. All of these qualities allow synthetic oil to hold up over a wider range of temperatures for a longer period of time than conventional oils.

Once you switch to synthetic motor oil, you cannot switch back

Many engines come from the factory filled with conventional, or “regular” oil, although the number has been decreasing steadily. Conventional motor oil is derived and distilled directly from crude oil. It is made up of molecules that are irregular in size and shape, and it contains more impurities than synthetic oil. Conventional oil does not last as long or protect as well as synthetic, and so, many auto owners (and vehicle manufacturers) choose to switch from conventional to synthetic oil.

But many motorists believe the myth that once you switch to synthetic, you cannot switch back to conventional oil. Though this myth persists, it simply is not true.

In fact, the two are compatible with each other. “Semi-synthetic” or “synthetic blend” products are actually a mixture of synthetic and conventional oil. So, not only can you switch between the two at any time (for what reason, who knows), but synthetic and conventional oil can be mixed together.

It is recommended that when you “top off” your oil, you use the same product that is already in your engine, but that has more to do with providing the best performance and protection possible. Once you change to synthetic, there is no need to switch back. But you could if you wanted to.

(Read What If I Add the Wrong Fluids To My Car?)

Synthetic oil is not good for cars with high mileage

Another persistent myth is that synthetic oil will not protect an older engine like it might a newer one. Again, this is not true. This story is rooted in the experience of some auto owners who added synthetic oil to their high-mileage motors and later found oil leaks. And that can happen, but not because the synthetic oil is bad for your engine.

Synthetic motor oil, being more consistent and flowing more easily – and containing higher-quality detergents designed to clean the inside of an engine – can present a challenge for an older vehicle that has not been well-maintained. Inconsistent oil changes (mainly with conventional oil) can lead to engine deposits and sludge – and the presence of acidic compounds. The seals in an old engine sometimes wear away without the owner realizing it because the old oil cakes up the cracks, holding the oil inside. The cleaning power of synthetic clears out the gunk, and sometimes leads to a leak.

But synthetic oil is a perfectly suitable option for a well-maintained older engine. It protects a high-mileage motor just as it does a new one. In fact, synthetics contain additives, conditioners to prolong the life of engine seals. If your older engine is in a state of disrepair, it might be best to have it repaired before using synthetic oil. But synthetic oil is an excellent option for high-mileage vehicles.

Using synthetic oil will void your new car warranty

Some folks believe that putting synthetic oil in their engine might void the new car warranty. That is not true. Unless you own a Mazda with a rotary engine, you can add synthetic oil in place of conventional oil.

Now, if you were to turn that around and suggest that using conventional oil could interfere with your warranty, you would be closer to the truth. Many automakers have made the switch to synthetic in their engines. If your engine came with synthetic oil from the manufacturer, you need to stick with synthetic oil for the life of the vehicle. Using conventional oil may void the warranty.

(Get answers to Mobil 1 Synthetic Oil Frequently Asked Questions)

Companies such as Mercedes, BMW, Honda, Toyota, Chevrolet, and more each have models (in some cases, all of their engines) that require the use of synthetic oil. Some oil viscosity grades (such as 0W-16 or 0W-08) can only be made artificially, synthetically. If your vehicle came with synthetic, make sure to stick with the manufacturer’s recommendation.

You can change your oil less frequently with synthetic oil

This idea presents a conundrum. One distinct advantage of synthetic oil is its ability to withstand thermal breakdown. It lasts longer – a lot longer – than conventional oil. Therefore, you should be able to travel a lot more miles between each oil change. And you can – as long as your vehicle is no longer covered under its new car warranty.

The length of time between oil changes for an engine is specified by the engine manufacturer. It is laid out in your owner’s manual or maintenance schedule. Intervals range from 5K miles to 10K miles or more, depending on the vehicle. Some “special” or “severe” driving conditions may call for shorter intervals.

Synthetic oil is able to protect your engine beyond what conventional oil can, to extend the time between oil changes. But your responsibility while your vehicle is under warranty is to adhere to the manufacturer’s recommendation. In that case, synthetic oil vs. conventional oil has more to do with advanced performance than it does with increased oil life (until your warranty expires).

Remember, always consult your vehicle owner’s manual for the type and weight of oil required for your car – and for the length of time recommended between oil changes. Then consult a trusted repair shop for their recommendation regarding the switch to synthetic oil.


This article is intended only as a general guidance document and relying on its material is at your sole risk. By using this general guidance document, you agree to defend, indemnify and hold harmless Columbia Auto Care & Car Wash and its affiliates from and against any and all claims, damages, costs and expenses, including attorneys’ fees, arising from or related to your use of this guidance document. To the extent fully permissible under applicable law, Columbia Auto Care & Car Wash makes no representations or warranties of any kind, express or implied, as to the information, content, or materials included in this document. This reservation of rights is intended to be only as broad and inclusive as is permitted by the laws of your State of residence.

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