well , oil is always a beaten up subject on forums. it is very important to my and my machinery. as of late i ran across some very good motorcycle oil at the wall-mart. Castrol 10-40 Racing oil for motorcycles. it is rated for wet clutches....so at 9 bucks a qt i changed out the 20-50 that the guy i got the bike from had in it motor was noisy!!! now with the new synthetic stuff it is quiet. runs stronger dropped a little in temp also. i figure the old oil was trash from sitting but i am however impressed with the new Castrol M>C>oil. i don't know if it is cheaper than amzoil.