Don't use it, you need a oil that is also good for the trans. Most automotive oils are not and would be wise to avoid them. If there is any friction modifier in the oil, it can affect the transmission in a negative way. The oil should also meet the 80W-90 GL1 gear lube spec.
I have a 2005 Rancher 400 AT 4x4 and I using Amsoil Motorcyle 10W-40 oil since about 25 miles. Now just over 1000 miles since March, I ride it everyday. No probems whatsoever. I am using the old version as I still had some leftover. I only change the oil once per year and being doing that since the 2001 model.
I also had a 2001 Rancher 4x4 and used the same oil in that for the complete time I had it.
btw-My Honda dealer sells Amsoil...as do most other ATV dealer around here. Very poplular (2 cycle) with the snowmobilers in winter. The parts guys told they sell a lot in the winter.
Go check out amsoil dot com and read up on it..if all else fails, use the Honda Oil. Caution Honda Oil filters are pricey, around 12 each and they gave me a discount. I found a Hasting model that is around $5-6, if you want the number I go out in the shop and take a look.
[ August 09, 2005, 09:49 AM: Message edited by: Mike ]