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Can You Mix Conventional Motor Oil with Synthetic?

Can You Mix Conventional Motor Oil with Synthetic?

Concerned about the health of your engine when mixing conventional motor oil with synthetic? Learn more about the risks here.
Dave Mann
August 5, 2020
5 min read
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Can You Mix Conventional Motor Oil with Synthetic?

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Meet The Author

“Hi, I’m Dave - a former Ford Truck/Automotive Engineer and the face behind Performance Oil Technology. My trucks, heavy equipment, farm and powersports vehicles experience extreme use, and I use AMSOIL products in every single one; learn more about me here. Have a question? Contact me here. Enjoy the site!”

Is It Dangerous to Mix Conventional Motor Oil with Synthetic?

In short, no. Mixing synthetic and traditional motor oil is safe, but we wouldn't recommend it. Diluting the performance of synthetic oil by mixing conventional oil with it will only detract from your engine's ability to run ideally. Read on to learn more.

Can I mix oil types?

Synthetic lubricants are becoming increasingly popular, which raises the question of whether synthetics and conventional oils can be mixed safely.

Many have been guilty of combining different types of motor oil without thinking twice in the past. Sure, the oil's performance was likely compromised, but the engine always survived because you can safely mix synthetic and conventional oil. Synthetic-blend motor oil is this exact combination, pre-mixed for you. However, we only recommend combining the two if it's an emergency.

Why you shouldn't mix synthetic and conventional oils

Regardless of its synthetic or conventional nature, all motor oil combines base oils and additives. Synthetic base oils are created using a process that removes the impurities characteristic of conventional base oils. 

Synthetic oils also usually contain higher-quality additives.

When it comes down to it, conventional and synthetic oils comprise the same elements, and they are compatible in theory. The elements in synthetic oils are simply of exceptional quality.

You can safely mix synthetic and conventional oils, but you're not helping your engine run more efficiently; you're just compromising the power and performance synthetics offer.

What if you have to mix oil types?

You may encounter a situation where you must mix the two types of oil, like if you're traveling. If your engine oil is low-quality and conventional oil is the only option, this is safe in the short term.

An engine that typically uses AMSOIL synthetic motor oil and is temporarily using conventional oil should be changed as soon as possible.

AMSOIL does not support extended drain intervals in which oils have been combined. Why would you want to add anything if you're already using the best possible oil? 

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