Between our various BMW, Mercedes, Corvettes, Audi & Jaguar vehicles in our family, we all use Mobil 1, Castrol, & Pennzoil synthetic oil 5 quart jugs of various viscosity of 0w20 to 5w30.

Since we don't always use the full 10 quarts of the 2 Five quarts, there's always a few quarts left over this 5 quart jugs.

So question is: Is it OK to mix between:
- different brands of synthetic oil (Mobil 1 + Castrol, etc...)
- different viscosity (0w20 + 5w20, or 5w20 + 5w30, etc...)
- different shelf life/age (been sittin' on garage shelf for 1 yr + 2+ yrs...)

Thoughts...?
Thanks,

 

IMHO mixing different brands of the same oil is perfectly OK, I have done it many times with zero problems.
But it must be the same type, viscosity and spec oil, for example full synthetic 5W-20 that meets the Ford WSS M2C925-A spec of the earlier AJ133.
That said I believe there would be no problem at all with mixing 5W-20 and 0W-20 as long as everything else was the same.

 

Oil AGE has no bearing. 2 years isn't THAT old.

I've heard stories that extremely old oil should be shaken (not stirred, LOL) before pouring, to mix the additives...but I can't see into the plastic jugs that well, so I can't verify if this helps.

Like OzXFR, I've mixed oils in the past on my daily drivers...never an issue. (For those cars I buy whatever brand is on sale so I commonly mix brands)

Early in my driving career I mixed oil brands in the car below, and it burned a lot until I changed the oil again using a single brand. But that was the only time.

Don't laugh...I was single, and the seats on that Classic folded, to make a bed. HOT STUFF!

 

My grandfather had a Rambler Classic for a few years!
And if memory serves it was the same colour as that one.
Extremely rare in Oz even back then let alone now.

 

+1.

 

I personally would not mix two different brands even if they both carry the same manufacturer spec approvals. You don't know the exact additives they contain and if they might negatively react.

 

I'd just be cautious. If you have 0w-20 six quarts and used 5w-20 for the other .5 or 1.25 ... not a crisis. But for the F-type just buy the Castrol in boxes of six on Amazon and always have extra. Anything you are saving $$ by not taking your baby to the *********** offsets any expensive oil, etc.

 

Never mix oils of different viscosities. When you mix a 0W-20 with a 5W-20, you don't end up with 2.5W oil. You end up with two different oil layers in your sump. Not good.

 

Really?!!!?
You mean the 0W & 5W will separate & layer ontop of each other, like oil & water?
& which one is on top? the OW or the 5W?

 

The only way they could or would separate is if they had a different specific gravity....do they??

 

Sorry, all synthetic oil is fully miscible. Even oils of different s.g. will just take on an s.g. somewhere between.

 

Interesting. So can I mix 0w20 and 10w40 to get to 5w30?

 

You’ll get something but the math isn’t linear and depends entirely on the viscosity index improvers used in each of the oils.

 

You should not mix oil.
First you have made a generalization- that synthetic is all the same. There are 3 different types of synthetics. Made from different ingredients.
The main reason is what are you going to put this concoction in? An old truck, chances are it will do terribly with 0w-20 oil. Or whatever mystery viscosity you end up with.

Here is what you can do with leftover oil.
Use it to flush our notoriously dirty engines.
Here is how, remove old oil, fill with concoction and lubegard engine flush, run for 5 minutes. Remove and fill new oil.
You wont believe how much gunk you get out, gunk that would oxidize new oil.

They actually make cheap oil for this purpose.

 

Personally I would never mix oils. If I were to, then it would be in emergency in an early car engine...pre microscopic tolerance and internal clearance days.

Any oil that is left over from a change goes straight into my oil cans for general purpose round the house/garage lubing.