I change my trans oil once a week when I clean the air filter. I usually go through ten to fifteen gallons of fuel in a weekend. Michigan has an extensive trail network and I ride a lot. I have used "Clutch Saver" "Gear Saver" and currently I am trying Dexon III. They all seem to function just fine.
I think the Clutch Saver bottle is the best looking and the Dexron is cheapest.
You will probably run into strong opinions with oil brand subject, I tell those people that I get my Dexron for free and everyone seems to understand free.
John