Depending on if you run a flat tappet cam or a roller cam you need to be concerned about ZDDP. I'm currently running Joe Gibbs in my 3 cars with flat tappet cams but when my current supply runs out I'm going back to Rotella 15W-40 diesel
oil as it meets all the necessary criteria. I don't see any need to run
synthetic in these cars that get limited mileage.
My opinion on
oil weight - I like to have at least 20 lbs pressure at hot idle in the summer. The lightest weight
oil that will still achieve that works for me. That opinion is worth not more than 2 cents.