But big $100,000 cars like this mid-range S-class Merc http://www.mbusa.com/mercedes/vehicles/model/class-S/model-S550V http://www.mbusa.com/mercedes/vehicles/m

But big $100,000 cars like this mid-range S-class Merc http://www.mbusa.com/mercedes/vehicles/model/class-S/model-S550V http://www.mbusa.com/mercedes/vehicles/model/class-S/model-S... seem to have 20+ gallon gas tanks (here's the S550's capacity http://autos.yahoo.com/mercedes-benz/s-class/2013/s550/specifications.html http://autos.yahoo.com/mercedes-benz/s-class/2013/s550/speci... ) and the ability to manage about 25MPG on the highway. That would place them at 500+ miles from a single fill. (They'll do a lot worse with city driving though: the S550 should only give 350 miles. I think these MPG numbers are the EPA's.)