The Environmental Protection Agency (EPA) does not a listed average for the 6.7 liter Cummin's engine; however, trucks that feature the motor see an approximate 14 miles per gallon, notes AutoTrader. Because 6.7-liter engines are used largely in commercial vehicles, heavy-duty trucks are not tested in terms of fuel economy.
The rough estimation is also based on driving habits and the condition of the vehicle. It's minimum fuel expectancy should not go below 11 mpg, and even drivers with the best habits are expected to reach a maximum of 17 mpg.
Although the fuel economy on these trucks is relatively low, the main draw of the Cummin's engine is its torque production. The stock engine rates 865 lbs.-foot.