There is a lot of rubbish written about ATV oils
For any ATV regular changes is more important than the oil used. Clean oil rules.
We put 500,000 miles on our trucks,without opening up the engine, changing oil every 4000 miles.
Nothing with friction modifiers is important
After that - it depends on the outside temperature - see owner's manual for list.
15-40 ordinary mineral oil changed every 100 hours will easily see 30000 miles trouble free onto an engine.
Change the oil filter with every oil change.
Don't overtighten the oil pan drain or filter bolts - Honda are prone to breaking, particularly 420s. Cheap bad design - no buts -- same as their transmission gears and dogs for the last 5 years, which are cheap, nasty, expensive and poorly made. So double the reason to keep them freshly oiled.