I prefer 10W30 conventional and that's why I go with the Valvoline VR1. Heard that going to synthetic may cause leaks. Michigan spring to fall driving only, so not sure if other grades would work as well and keep the oil pressure where it is at currently. Not a mechanic by any means. Just what I've always used and kind of stuck to it, hence the conventional VR1 instead of other racing oils. Heck, first few years I owned the car I was using regular conventional until someone mentioned racing oil with higher zinc.