Make sure you add Fuel Additive to the engine and fuel system in your 2004.5-2005 Chevy/GMC 6.6L LLY Duramax at every fill-up. Additives are specially formulated to provide your vehicle with the ability to clean and maintain the components in your engine and fuel system, reduce smoke, and improve engine performance. In addition to additives that enhance lubricity and cetane, other additives are designed specifically for cold weather and to reduce fuel gelling and provide winter protection. Find the additives you need in your vehicle from the top brands like FPPF, Hot Shot's Secret, Lucas Oil, XDP, and more!