Originally Posted by TopDollar
Will Castrol Syntec SAE 75w-90 gear oil work for the gear casings on my ATV? The book calls for Honda SAE 80 hypoid gear oil but that stuff costs 4x what the Castrol does.
You need to post in the Honda forum. A non-Honda owner might stear you wrong!
First and foremost, the oil must be HYPOID specific. Hypoid gears are very hard on oil, so it needs a very robust anti-wear additive package. As I recall, either GL4 or GL5 is ok. Honda's own oil is called Shaft Drive Oil and is 80W85. The diff and final drive only take a scant few ounces and don't need to (usually) be changed very often, so I can't see why price would ever be an issue for anybody who can already afford the purchase price of even a used quad.
Personally, I run Maxima ester based 100% Syntlhetic Gear Oil, 75W90. In my Ranchers I change it about twice a year, and once a year in the 250's.