The energy required to push a vehicle through air goes up as a CUBE of vehicle velocity. ...

Disclamer:

I didn't stay at a Holliday Inn Express last night and I pawned my slide rule today to buy gas. However, I did race on asphalt for chuckles. The rule of thumb says that any 3300-pound sedan with 100 net horsepower will run 100 MPH on a flat track at sea level, and that air resistance isn't a major factor until you reach 100 MPH. Faster than that and you start compressing the air in front of the car to move forward.

Then to increase forward momentum by just 10 MPH you must up Horse Power production by 25%. Take out your el cheapo calculator and do the math, 100HP X 25% + the product = 125HP; X 25% + the product = 156.25HP;... do this 10 times or until you reach 200 miles per hour. You'll find your making 600-horse power by the time you reach 200 MPH, which is about the top speed of a NASCAR cup car. In addition, any NASCAR cup type driver will claim he has 600HP under his hood.

On the other hand if you're drag racing, the rule of thumb says the best way to decrease your elapsed time by .10 (1/10) second is to lose 100 pounds of dead weight off the body, frame and running gear. No additional power or fuel is needed, just less weight to move down the track. Therefore, I believe weight is the greater waster of fuel, especially in an internial combustion gasoline engine.