Cummins mpg vs 225 Slant 6 mpg

I am a slant guy but being that we own two Cummins powered trucks, I'd have to go that route hands down. Dad's '01 24v gets an easy 20+mpg anytime. The only slant vehicle I have seen get better fuel economy than a Cummins is dad's Feather Duster. Power and mpg go to the diesel without question.