Any gear oil rated GL-5 of appropriate viscosity would be fine

Here in the desert southwest I use 75w-140 syn.

 

This is an old thread, but I have a similar question. I have some new and old bottles of Castrol 80w90 gear oil. Both are GL-5 but the new bottles say limited slip and the old bottles say hypoy C. Is there any significant difference and can I mix the two types?

 

If it were me, I would NOT mix the two types.
I personally, if it were me, again, would use the Hypoid version. That's just my opinion, for what it's worth. As long as it's GL-5. THAT'S what matters most, but I don't know what effect mixing the two different types would have.

Of course, on the other hand, the newer the better, but I believe, as long as they been in the factory sealed bottles, it won't matter. I may well be wrong on that, though.

Good luck, whatever you choose.
Pat

 

Thanks. The old hypoy C bottles that I had were not sealed, but were kept in my workshop at house temperature. They were several years old but I decided to use them up. I only had to mix about 1/5 of a quart of the hypoy C with the 2 quarts of new oil in the rear diff. The front diff, I used the remainder of the hypoy C (no mixing).