Just to muddy the waters even more, we'll have to consider these two additional forms of 'drag' in the mix.
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* 'Curve Resistance' is something investigated by General Motors Corporation during the golden years of MPG research, considering :
- Velocity
- Radius of road curve
- Superelevation of curve
- and Weight of vehicle
( with a 76,000-lb semi, on a 108-ft radius, at 20-mph, the total additional retarding force due to the curve was greater than the total retarding force on a straightaway at the same speed )
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* 'Grade Resistance' was researched by Chrysler Corporation, as a tool they used to win ( cheat ) the Mobil Economy Run, three years in a row, by pre-determining an optimum speed for ascending grades of different magnitude, based on a hidden inclinometer.
( if you lift 550-pounds, one foot, in one second, your accomplishing 1-horsepower worth of work ). On an uphill grade, you're lifting the vehicle's weight some distance ( in feet ) per second, which is converted into a horsepower penalty the engine must absorb. If the Silverado were a hybrid, on the 'downhill', 81.1% of deceleration kinetic energy could be pumped back into the battery.
