Honda recommends changing the oil in the rear drive and front differential EVERY 2 YEARS. My experience has been that that isn't nearly often enough! My personal interval has been about every 6 months.

I changed out the brand new Rancher 420 after ~4 hours of break-in riding, and there were surprisingly quite a number of metal flakes in it! Last night changed I out the Rancher 350 which was done about 6 months ago, and there was some metal in it as well. Front diffs on both were very very clean.

Haven't done the 250's yet this season, but in the past they have had some metal in them as well.

This is an easy job, so you may want to consider doing it more often than every 2 years...........

 

oil looks as new as the day i put it in. i was changing once a year, but there is no point. has no metal or even close signs to any break down. i will be going to 2 years.

i also had my rear diff apart due to a water issue, and there aren't even marks on the ring or pinon gears. like they just came off the assembly line. oil changes definitely don't need to be increased