theres a ton of oil debates on which is best for the ltr on ltr450hq.com i have ran amsoil because i got a case from a friend but many many ltr owners seem to be running shell rotalla T 15w-40 i believe and they change it as much as they can because its cheap as hell. i will probably make the switch myself. just some thought, to each his own. its an awesome bike, still nothing to this day on the market like it...lots of luck
and listen to kennerz about that O ring on the oil filter