Better gas mileage

I also think that weight has more to do with MPG than aerodynamics. If you look at the front of a C with the overhang this is much less aerodynamic than an A but shorter C's will have better fuel economy than a longer A because they are much lighter. Longer length equals more weight. If the C and A are the same length and weight the A may be slightly better. Now I realize there are other factors that come into play such as gear ratios, HP to weight ratios etc but for the sake of answering the OP she is right longer is heavier and heavier is less mpg. Another simple example is just compare Class A's with the same front ends in a 28 ft and 38 ft and you will see the 38 ft gets less mpg over the 28 ft.