If you are using a GM crate motor or even some builders engine, they should specify a letter grade as well as weight grade. Brand name - if it's a flat tappet engine, then you want one like Joe Gibbs or Brad Penn that has more of the zinc compound, ZDDP. If it's a roller cam engine, then any of the national name brands will work just fine. The Mobil 1's, Lucas's, Amsoil's, Royal Purples - IMO are fine but way overpriced oils which good advertising has cast an expensive ($10-$12/quart+/-) spell on the buyers.