well i use M1 15-50. it saw 250-300+ all weekend w/ 250+ water temp all weekend. the oil still looks new. so new i can still barely read it on the stick. i'll stick w/ M1 for the availability @ your closest wal-mart or parts store. i have no problem w/ RP but the lack of it being commonly available. i think 0-40 was you 2nd problem w/ the first being $70 ARP rod bolts not being used. i'll upgrade bolts before rods any day.
|