A: For a diesel engine, use Diesel Extreme every 6000 miles to clean the injectors and fuel system, and EDT at each fill-up for a cetane boost, injector maintainer, water dispersant, rust and corrosion inhibitor, plus lubricity and fuel stabilizer. For the oil system, use Stiction Eliminator to clean the burnt oil "Stiction" in the engine, and then FR3 to protect it.