[aerohead]

I ran the numbers for the Impreza dimensions.
The frontal area is approx. 23.815- sq-ft ( 2.212 meters-square ).
The L/ sq-rt of Af basically doesn't change.
'Kamm's' V-criteria does, increasing to 2.4643.
A comparison of seven cars with V's in the neighborhood, averaging 2.3372 yielded an average Cd 0.1475.
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If the car were given the TF wheel covers and tail as a 'new' car, over it's statistical, 12-year lifespan, for the EPA-weighted HWY portion of it's total mileage, the Impreza would return:
* approx. 600-million less Btu waste heat to the atmosphere ( entropy )
* 5,274 fewer gallons of fuel consumed.
* @ $ 3.00/gallon, saving $ 15,800.
* And lowering carbon-dioxide emissions by 52-tons.
The fuel savings would cover about half the new car price, in constant dollars.