New to the Diesel huh? You're going to LOVE it! I use Rotella T, my brother prefers the Chevron stuff in the blue bottle. Just be sure it is Diesel oil because it is specially formulated with detergents for our motors. If you came from a gasser you can forget about buying quarts. It's all in GALLONS now! I buy it buy the case. Stay up on the fuel filter too! Very important! Every 15K.