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Synthetic and Conventional Motor Oil

If I have to add a little oil between changes, is it okay to mix conventional oil with synthetic? Or, should mixing be avoided?

You can mix them.

After all, they sell synthetic blend oils. A mix of conventional and synthetic oil.



Thank you very much!

Hold on a minute. It depends on the car and how much conventional oil you are adding. Many new cars require 0w20 synthetic, you should not add conventional, but in an emergency it would be better to have some conventional than no oil at all. Just get it changed ASAP.

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Keith makes a good point. If your car requires synthetic oil, conventional oil is better than no oil, but you really should make an effort to only top such a vehicle off with synthetic oil. You don’t want to void your warranty or ruin a turbo with conventional oil.

If the car only requires conventional oil, but you’re using synthetic oil for some other reason, it’s fine to mix them as much as you want.

I always have a quart of the proper oil in the trunk and the funnel to put it in with just in case. I have even recycled brand new oil that I couldn’t use anymore.

I drive a 2005 Buick Century. My owners manual says to use a 5W-30 motor oil that complies to GM6094M specifications. I researched that number and found a long list of motor oil brands and varieties; conventional, synthetic and synthetic blend.

Then you can use any 5W-30 with the API certified label, which includes all name brands.

…and most generic or store brands.

Very true, but there have been a few instances lately of bad oil in ‘dollar’-type stores or convenience stores. Not knowing the OP’s experience level, name brands are a safe bet.

Mixing a quart of conventional oil when the crankcase contains synthetic is about the same as having a shot and a beer.

…because it never ends well?

…with me hugging the toilet and promising never to drink again?

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