Personally, I have never needed to change the o ring in the last 17+ years across multiple quads. The filter I have used forever is HF140 by Hiflo Oil Filters (I buy 10 packs from racing powersports). I do change the crush washers for the drain plug every so often because the older they get the harder you need to torque the bolts. I also change my oil at least every 10 engine hours or after every race.