[Big Dave]

Step back from the graphs a second and think about what you are saying.

How is it that a Dodge Ram with a Cummins engine gets 50% better MPG than the same truck with the same transmission and the smaller and lighter Hemi?

How is it that the VW Jetta with a manual transmission gets 33 MPG where a gas engine in the same car with same transmission gets only 22?

I think there are a lot of “apples and oranges” in the published BSFC graphs.

The only performance downside to the Cummins four is its weight. That engine weighs about the same as a Ford gas V-10.