Rotella 15w40

There's plenty of data out there. Bob's the oil guy, etc. Rotella has as much zinc as most shelf street (non-race) oils. I've never had a bearing, lifter or any other type of issue that would be considered "oil related" and the motor's always look good if you take them apart. Race car will be a different story. Everyone has their preference. It's worked well for me, even on air-cooled motorcycles in the heat of summer.