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Originally Posted by tsanto  I dont know much about aerodynamics but on a modern car the difference in 65mph and 75mph cant be that much in gas milage. |
The second statement certainly verifies the first in your post.
The aerodynamic drag force on a moving object goes up with the SQUARE of the velocity.
For example, if the drag force on an object were 100 pounds at 50 miles per hour, it's about 260 pounds at 80 miles per hour. I.e. the force is 2.6 times the first even though the speed is only 1.6 times the first.