OK to mix old synthetics?

[austai]

I found some bottles of unused, unopened synthetic oil from a few years back, some maybe 5 years old, from different companies. Is it OK to use them? Is it OK to mix them? They'll be used in a Miata so it's not a real stressful application vs., say, a turbo, but I'm still a little nervous. OTOH, I don't want to just waste them.

Thanks

 

[Mr Magoo]

As long as they are sealed, there will be ZERO problems mixing oil that is only 5 years old.

I recently found SJ rated Pennzoil in my brother's garage and I used it . I didn't worry about it being 8 years old.

 

[Pablo]

What brands?

 

[Audi Junkie]

I'd keep the old M1 seperate and mix that with new M1. The other old stuff I'd mix toghther and top-off or add plain dino oil to fill.

 

[austai]

OK, here's my collection of oldies but goodies (?)

mobil 1 0-30 SJ/SF
penzoil 5-30 SL
penzoil performax syn 5-30 SJ
castrol syntec 5-50 SJ
havoline syn 5-40 SH

I guess I was trying out different oils over the years and had leftovers.

So, any above I should avoid mixing with the rest?

Also, would a good dino SM oil today be better than these old synthetics? If yes, I'll just give these away to my brother who drives a corolla and doesn't care about oils.

 

[bruce381]

dump them in for a 1,000 mile "rinse" then go back to 1 brand mixing may not hurt at most some VII may fall out when cold.
bruce

 

[Audi Junkie]

Keep the M1 for use with some more fresh SS M1. Mix the Havoline Synth with regular Havoline/Chevron...I mix it with Delo, all quite similar.
The Pennzoil and Syntec are all probally G-III base, that's what I'd use in a soup.

 

[pbm]

I wouldn't mix different brands of synthetics in case of compatibility issues. On the other hand I would have no problem using old SH, SJ, or SL rated synthetic oil. I don't think oil goes bad like milk but rather as Bruce381 said it may have some VII fallout. I think even this is minimized if the oil is unopened and stored at constant
room temp. I would add one qt. at a time to your favorite dino preferably of the same brand. It won't hurt a thing.