I have a '99 Kawasaki 1500 Drifter with 27,000 miles on it. I changed oil in it a year ago last October and have put less than 4,000 miles on the oil change (Amsoil 10W40 MC oil and Amsoil's best oil filter). Amsoil says to change at one year no matter what the mileage. I get my oil and filters...