Duramax vs Power Stroke Fuel Economy Tow Test and Drag Race

4x4ord wrote:


It would be interesting to see the brake specific fuel consumption graphs for these engines. You'd expect the transmissions to shift according to fuel usage.At 1800 rpm these engines can produce over double the power that is needed to tow a typical 5ver down the highway. I'm surprised lower rpm wouldn't save a little fuel. A general rule is that higher cylinder pressure produces greater efficiency. If you're running higher rpm than is needed the engine is operating at a lower cylinder pressure than it could be.

On flat ground under low load the fuel economy is better in 6th, but on hilly roads, a lot of wind resistance, or in other situations that put more load on the engine it is is not in my experiences. In 6th and under higher loads, it feels like the engine has to add more fuel/air to compensate for the lack of torque from a taller gear ratio and the lack of horsepower from being at a lower rpm. In 5th, it feels like it does not have to add that much fuel(fuel pressure is lower) and boost to do the same work. There is less load on the engine in 5th even though it is at a higher rpm. There is also the factor that EGT's are lower by about 200F as well.