AMSOIL first in synthetics
Nick King
Liberty, MO
CALL (816) 550-5556


 The simple answer: Yes. There is no danger mixing synthetic and conventional motor oil; however, conventional oil will detract from the superior performance of synthetic oil and reduce its benefits.

The detailed answer: With synthetic lubricants continuing to grow in popularity, the question of whether synthetics and conventional oils can be safely mixed often arises. I’m guilty of having mixed different types of motor oil with reckless abandon back in the day. A dash of synthetic blend to top-off my early 90s Buick Century one month and maybe a shot of cheap conventional oil the next. Though I’m sure performance suffered some, my engine never blew up as a result. So, yes, you can safely mix synthetic and conventional oil. But barring an emergency, it’s not a great idea.

Compatible components

All motor oil, whether synthetic or conventional, is a combination of base oils and additives. Synthetic base oils are manufactured using a process that removes the impurities inherent to conventional base oils. Synthetics typically contain higher-quality additives, too. So, in the end, conventional and synthetic oils are comprised of the same, compatible components – it’s just that the components in synthetics are much higher quality. While you can safely mix synthetic and conventional oils, you’re doing nothing more than diluting the performance of the synthetic oil. You may not have a choice in some cases. If you’re traveling, for example, and suddenly find your engine low on oil, cheap conventional oil may be the only option at the gas station alongside the highway.

While it’s safe to top-off an engine that normally uses AMSOIL synthetic motor oil with conventional oil, we recommend changing the oil at your earliest convenience. In fact, AMSOIL does not support extended drain intervals where oils have been mixed. When you’re using the best oil available, why add anything to it?

If you’re looking for the most reliable synthetic oils or just need more information call Nick with Missouri Synthetics at 816-679-1599. Be sure to check out our online shop for all your oil needs, including motor oil, fuel additives and filtration products.
We will get back to you as soon as we are able.


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Liberty, MO 
64068 United States
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