I use mobil 1 motorsport 15/50 its done a good job in my cossie and my rs turbo. on the subject of cam follower rattle if using correct grade of oil its going to be the followers.I have built a few cossie engines the ones that had new aftermarket followers in started to make noise on start up again after abut a year.I was lucky enough to find a new set of kent cams ones on ebay cheap these are still quite even after months in the garage untouched