OK to create your own synthetic blend?

[kreativ]

I have a few bottles of SL-rated oils left over:

3 qts. Castrol GTX 10w30
1 qt. Valvoline Synpower 5w30
1 qt. Havoline Synthetic 5w30

My Toyota V6 3.0L takes 5qts. of either 5w30 or 10w30.

Can I use these oils together to create an 8w-30 synthetic blend? Or is mixing different types/weights/brands a bad idea?

 

[JohnnyO]

I don't know that it would actually create an 8w-30, but it wouldn't hurt. Not something I'd do all the time though since you're not really sure what your getting (unless you do some MSDS digging, which some BITOG'ers will do

). Right now my van has 3.5 qts of DuraBlend and 1 qt of Synpower, both 10w30, because I had some syn left over from my mother's car.

 

[Ken2]

The viscosity you end up with is not the arithmetical average. The only way to know the mixed viscosity is to test it.

Different brands of oils, and different lines of the same brand, may have different additive packages. They're all "compatible." They won't turn to black gum or anything bad, but they might not be as good as just any one of the single brands might be. I'd save the single quarts for the neighbor's lawnmower or somebody's emergency low oil, or something else, and buy what I think will work best for my engine.


Ken

 

[Triple_Se7en]

I'd use that combination with no 2nd guesses. The only difference between that and any other synthetic blend oil change I've done would be a shortened OCI. For me, I would probably change it after 3000 miles instead of my usual 4500 due to unsureness about additive mixing & how it counteracts while aging.

Incidently, all my GMs take 4.5qts. When I blend, my ratio is usually 1.5 synthetic & 3 dino.... 33.3-66.6%.