Thanks for the info on this topic guys. I used Mobil 1 the other day in my wife's new Montero Sport(second oil change), this is probably what I will eventually use in the quad. I will use their atv/motorcycle oil. One additional question- is the filter for the 500i the exact same filter as the Vinson or is it different? I asked two different stores about this(neither of them sold Cats but they did sell Suzuki's) and they couldn't tell me. Thanks