Jay4200
Veteran Member
- Joined
- Nov 23, 2005
- Messages
- 2,028
- Location
- Hudson/Weare, NH
- Tractor
- L4200GST w/ LA680 & BX2200D w/ LA211
The fact that 80-90 is heavier, is a very popular misconception. The 80-90w suggests it's heavier. It's not. Gear oil is not tested on the same scale as motor oil.
Do some research, and some pour tests, and you will see it for yourself. The differences are not substantial.
The actual viscosity, between 80-90w gear oil and hydraulic transmission oil, at room temp. is basically the same.
Both are light weight gear oil, which is why they are interchangeable in this application.
80-90w gear oil, hydraulic transmission oil, and 30w motor oil are all similar in viscosity. With much of the differences being that viscosity's do vary. Any two 30w motor oils for example, will have different viscosity's.
An EP gear oil, offers the highest degree of protection for hypoid gears. (The kind in a diff.). So, it would be best by that standard, if you have the option.
Is it necessary? Probably not. But, if it's only 2 quarts. And, someone wants to go all in, it's a good option.
If someone is worried about cold weather operation, there is such a thing as synthetic gear oil, for a couple of bucks more. Win, win.
Actually, gear oil IS thicker. UDT viscosity is roughly equivalent to 15wt motor oil (SUDT is 10wt) and 80W90 is roughly equivalent to 30wt motor oil. Just sayin'.
JFTR, I use 90W140 in my L4200's front axle because one of my bevel seals leaks like a sieve.