Being a born and bred, dyed in the wool, smoker advocate (diesel engine freak), I had the opportunity in Canada to take a diesel Smart for a ride... OMG... it might have given us decent mileage but DAMN, was it underpowered... 70mph was a longgggggg way down the road... might work as a metro buggy but on the highway.... no, no, no... as for the gas I've heard the same thing.. mileage wasn't what the owners expected it to be... think I'll keep riding my Wing.