Synthetic. No question. Better at everything
oil does for your engine.
I say this assuming that your engine is fully broken-in. Run dyno
oil for 2500 miles or so to seat the rings and then make the switch to
synthetic. Flat tappet cams need a
zinc additive, whether
synthetic or not.
I also recommend synthetic tranny and rear axle lube. Will run quieter, cooler and last longer. Garrooonnnteeed.
