Amsoil lubricants are the best that money can buy. I put that same 75W-90 gearlube in my '88 Jeep's rear axle in 1989 and it lasted for 970,000 miles. That vehicle now has over a million miles on it and that rear axle is still untouched. Now, I wouldn't advise leaving it in for 30 years the way I did, but it's a testimony to the outstanding performance that Amsoil products deliver.