A GMC 2500 HD Duramax Diesel gets a combined average of approximately 15 mpg. The Duramax's fuel economy rating manages to be 50 percent better than its competitors, according to Truck Trend magazine.
The Duramax uses a turbo-diesel engine, which helps produce more power and better fuel economy than its petrol-fueled competition. Although the fuel economy average is 15 mpg, that number is subject to change according to how the vehicle is used. Duramax trucks that are used to tow large objects may see an increase in fuel consumption.
The best way to ensure the Duramax's optimal fuel economy performance is to stay on track with the engine's maintenance and service procedures.