Do you have to use honda oil in a honda 4-wheeler?

No

No better or worse than any other major brand oil. Honda does not refine oil, they buy it from a major oil company that puts their name on the can.

i have always used same as goes in car----10w-40. or the new semi sinthetics will do. iv had it from new {1981} and engine perfect. out on it today.

I own a 2000 model odyssey, and have purchased the shop manual for it. From all indications, which include this manual and numerous internet searches, the only 'safe' fluid to use is Honda ATF-Z1,...

Pull the skid plate from under the engine off. makes access easier but isn't required. there is a bolt on the bottom of the transmission/crank housing. open that up and oil should come pouring out....