#1, Honda doesn't make oil, it's just re-branded for them, check your manual..the thing you read to learn all about your engine, mine(25) can use 10/30 or 10/40, you can get filters at CTC, about $5.00 instead of $15 at Honda. Whats the point of dumping new oil in a dirty filter. Some of the series use the same filter as the motorcycles.