Fuel mileage of Diesel engines

[CP194849]

I'm in the process of shopping for a used diesel pusher. Would appreciate input on the following: All things being equal GCVW, etc, is there a substantial difference in fuel mileage between a larger engine I. E. 400 to 500 HP and a 300 or 330 HP engine

[rexabbot]

I don't think so.
My 300 hp Cummins with turbo boost to 400 hp gets 7-8 mpg.