Do gear oils mix ok?

[Hollow]

Due for a diff service on my Subaru.

Front takes 1.2 quarts, rear takes .8 quarts.

I currently have a single bottle of Valvoline Durablend 80w90 and a single bottle of Mobil 1 LS 75w90 gathering dust on a shelf.

Ok to mix a little of one into the other for the front diff? And which would you put where? The subaru has a sealed limited slip in the rear diff, so it does not require an additive. Only spec it needs is GL-5.

 

[MichiganMadMan]

It's funny you would ask that, my Subie repair manuals specifically warn against mixing flavors of gear lubes. Got a motorcycle or bicycle? Buy another quart of whichever one you like the most and use the rest as lube for something else.

 

[JPP]

Originally Posted By: Hollow
Due for a diff service on my Subaru.

Front takes 1.2 quarts, rear takes .8 quarts.

I currently have a single bottle of Valvoline Durablend 80w90 and a single bottle of Mobil 1 LS 75w90 gathering dust on a shelf.

Ok to mix a little of one into the other for the front diff? And which would you put where? The subaru has a sealed limited slip in the rear diff, so it does not require an additive. Only spec it needs is GL-5.


*** I mixed those EXACT same lubes in the front diff of my '02 Silverado because I had enough of each around. And......... it runs just fine. Used 4WD several times and nothing grenaded. LOL
Anything was better than the mess that I drained out!

JP

 

[Eddie]

Many manufactures say Don't mix gear oils. I would not take a chance to save dollars.

 

[JPP]

Originally Posted By: Eddie
Many manufactures say Don't mix gear oils. I would not take a chance to save dollars.


*** I am NOT trying to start a big fight here.... I promise.
I would like to have scientific proof that this is a big deal. I think folks thought this way about motor oil a long time ago and by now we all realize that if your car holds 6-7 qts of oil and you use a 5qt jug of one brand and top off the last 1-2 qts with another brand it is perfectly okay. My front diff has 2/3 Durablend and 1/3 M1. IF this is for some reason a proven problem with the data to back, I want to know so I can change it out! I would bet that is not that big of a deal but am perfectly ready to be educated.


JP

 

[exranger06]

I mixed some Napa conventional 80w-90 and some Valvoline synthetic 75w-90 in my Explorer's rear end several years and 40k miles ago. It's still in there and running fine.

 

[camelCase]

Look up the MSDS.

If the major ingredient in both is hydrocarbon base stock - mixing will be fine.


Some additives can't mix and all that jazz - but the big key is the base stocks.

Like base stocks are compatible. Some non-like base stocks are too. However - if the two major components are different (like one is a PAO base and the other is a hydrocarbon base) - let us know what they are because they might not be compatible and will turn into a nasty gunk inside your diff.

 

[Ken2]

Huh? When millions of cars and trucks go in for service and the gearbox is a bit low, the shop adds whatever brand of gear oil they got the the best price on that year. Those millions of cars and trucks continue to run fine.