Milton, for more years then I care to remember, I used only Valvoline, about 4 years ago I started to use Shell Rotella T in all my engines (not the bike) and like everyone else, worried about not enough zink, and phosphorous.I wonder if the north had anything to do with the way Quaker State and Pennzoil would react in the motors? this was back in the 60's however, and not racing oil....
john
