The 300na engines are geared taller than the 240 but were only offered with automatics in the us. the turbo engines are geared taller. I think they all would deliver similar mileage if geared to take advantage of what tranny is in the car.

I had a us 240d car which I put in a euro 300 n, 307 rear end and five speed od stick. It would deliver 40 mpg with regularity highway if not driven too fast....say 65. That car would go 100 mph in fourth or fifth gear.

I also had a 300cd which I put a four speed stick in and I believe given the same gearing as the na it would do about the same economy with the turbo.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.