Always broke my motors in and first couple of trips to the track on Shell Rotella then switched to Mobile 1 15-50. 15 years and 3 engines I only had to put in new bearings once in one (the stroker) and one timing chain and the only part that I ever lost was 1 alum roller rocker, probably out lived itself. Mobile 1, in my opinion, is as good as most any out there. The best oil on the planet cannot replace quality machine work though.