I'm going to be changing my tranny and diff fluid soon and was wondering if I can use the half bottles that I have leftover from the last change three years ago...

The fluid is Redline MT-90 (trans) and 75W90 (LSD) for an '88 GTU. The fluid was kept in a cabinet in my laundry room, so not exposed to any freeze/thaw cycling, etc.

I'm guessing I should probably toss the old stuff.

 

I'd run it.

 

I wouldn't think there'd be anything wrong with it. It's oil, not milk. It's already spent a few million years in the ground and it didn't spoil then.

 

it should still be good. Theres nothing really contaminating it if its kept in the bottle. Ive used unopened oil on my car that has been sitting in my basement for who knows how long.

 

A reply on a different forum suggests that it will absorb some water, which will then be released once the engine/diff gets up to temperature.

 

hmm never knew that.. even if its never been opened?

 

Even with the lid on there is atmosphere inside the container. But that's a quantity of moisture that I would expect to be beneath concern.

 

I guess for the quantity involved (about 1/2 quart each of the MT-90 and 75W90), I'll probably opt to recycle it rather than use it. Thanks for all the replies.

 

Oil has a shelf life of about 5 years. Before you pour it into your car, make sure it didn't separate inside the bottle.

 

pfft, there's children starving around the world who could use the money you spent on new oil when i'm sure the stuff you have is perfectly fine.

 

if you threw it out you would be wasting money. If it got a little mositure in it, which would be mircoscopic if it was sealed and stored well like you say. i wish I had money to throw away...

 

So if oil has a shelf life of about five years, does this mean if I use it now, it will begin breaking down inside my transmission in about two years (since it's been on the shelf for three already)? Since I generally drive only 5000 miles a year, I'm on a schedule of changing my gear oil every three years. So does that mean I'll need to change my gear oil sooner if I mix in the old stuff?

Believe me, I'm not in the business of throwing away money. My wife still looks at me funny when I show her perfectly good stuff I've fished out of the neighbors' trash. But I'd rather throw away $10 worth of oil than use something that's going to harm my car or work less effectively.

 

just put it in

 

That's what she said.

 

gear oil is not brake fluid. just because you broke the seal, it will be good for a couple of years.

so, yea, use it.