how to identify gear oil

While starting to get organized in the shop last night, I found two gallons of gear oil that I never opened. The labels are faded to solid white or have fallen off.

Any way to tell what weight they are? Or should I just dispose of them? Any good uses for unidentified gear oil?

You could send a sample to Blackstone.

You can use it as a chick repellent.

Color will narrow it down to synthetic or non. Otherwise i have no clue. We use old gear oil for leaking diffs on random things.

Pickup truck axle lube. Drill bit oil. Put it in a oil can for whatever purposes. Give it to a farmer to oil their machinery. Dump it on the pavement and do smoky burnouts.

For what you probably paid for it, I would be tempted to recycle it.

I actually need to change the rear axle oil in my truck. does it really matter what weight it is for that purpose?

and if it does, ill follow the shop use suggestions of gearheadmb. im not spending the money on blackstone.

honestly, I was kinda hoping that id get the answer of a gallon of 75-90 weighs XX.X and 90-140 weights YY.Y.

If I really had to know, here's what I'd do. Buy a new bottle of gear lube. Drip a little oil out of both bottles onto a piece of sheet metal or something else that's smooth. See how the oil runs down and compare the two. Beyond all that, hey, it's gear oil. So what if one bottle's a little thicker than the rest? It only comes into play in the dead of winter anyway. Just be sure it's gear oil and not ATF.

What does it taste like?

I think that the only potential problem comes down to whether or not it has friction modifier in it, and whether or not you need friction modifier for a limited slip.

Unknown about friction modifier, but the truck is a peg leg so it doesn't matter.

Im not concerned about cold. It only ever gets to single digits hete a couple times a year. Im more worried about the big number. But according to manufacturer, truck calls for 75-90. If the big number is 140, it won't hurt anything.

And im sure it's not atf. I had never bought atf prior to buying the house, and the jugs moved in with me. Which means that they have been kicking around for greater than a decade. Wow.

Thanks guys.

You'll know if it has friction modifier in it. It really stinks. Love the smell of hypoid oil in the morning

spitfirebill wrote: You can use it as a chick repellent.

That stank,skank repellant.keeps the kooties off.

I'd send a sample to Blackstone labs to ID it.

Go buy a bottle of 75w90 and bottle of 75w140. Pour it all out of each noting how thick it is/how hard it is to force out through the little spout on the end.

Now fill a bottle up with mystery oil. Do the same through the same pouring spout/cap.

And guess.

What kind of truck? Most stuff won't care if its 75w90 or 75w140.

It's a 64 el Camino. Im fairly certain it won't care.

And I do have a few partial bottles of labelled gear oil. I like the educated guess method you describe.

It absolutely won't care

The GM 10 and 12 bolt read ends had fluid weight specified differently usually for towing purposes. It will all keep the bearings happy though.

If it's not sparkly, it's not what my truck uses.

Assume its cheap LSD 80w90 and act accordingly, not like the stuff is all that expensive unless you need 75w140. Gear lube also makes pretty good penetrating oil thinned out with petro paint thinner or gas, EP additives keep things from galling.