I know that this question has probably been asked several times however I haven't been here that long. My 600 xc/sp valves get really filthy and just the other day it took me almost 2 1/2 hours to clean them. My local dealer said I could use amsoil and another polaris rider said no use yamalube. I was thinking of blue marble?? Any insight an what is ok to use I don't want to have to clean them off after every ride. They were just caked with carbon really bad.