[Vwdiesel] Why gasss cars mpg sucks

[Roger Brown]

H . Hagar. wrote:
> Going back to old tests I did in a Rabbit (IDI), the lowest cost 
> per mile happened about 40 to 45 MPH.  Slower than that, and the 
> fuel cost per mile went up, due to powerplant inefficiency.  Faster
> than that, and the aerodynamic penality went up.  The trades 
> for uphill-downhill are different, but they are still there.
> Aerodynamics are a big factor, powerplant performance is a bigger
> factor, but rolling resistance is not.  (Rolling resistance is not
> the trade of kinetic energy for potential energy that happens when
> you go uphill.)

I recall an article I read many years ago in Popular Mechanics where they found that they got the best fuel economy with a 
driving technique that involved driving around that speed range.  But the twist was to use a varying speed, accelerating at wide 
open throttle from about 30 up to 50 then shut the engine off and coast back to about 30 then fire up the engine and accelerate 
to 50 and repeat.  I recall this was on a gasoline engine.  But the idea was to just run the engine flat out when it was running 
then shut it off in between.

I find aerodynamics is a big factor on my Caddy, at 65 and above, I get around 36-38 MPG, but hold the speed to 55 and I get 
around 44.

-- 
    Roger