A 20% reduction in drag = a 10% increase in fuel economy ?
 

So I seem to remember it being said that a 20% reduction in drag = a 10% increase in fuel economy above 55 mph .

Is this correct ?

Yes

intredesting...:turtle:

So if I take my 1993 Civic hunchback with a stock Cd of .31 and drop the Cd by 60% down to .124 , then my fuel economy will rise by 30% ?

42 MPG highway + 30% = 54.6 MPG ?


( yes - I completely FAIL at math )

If you can take your Cd down to 0.124, then you should be getting a LOT more than 54MPG.

0.124 is ... ridiculous.

Right. I'm doing the math wrong .

Aero Civic is ~0.17

95mpg at 65mph

That's what I'm not understanding .
How much of that number is due to aerodynamic modifications, versus coasting along in neutral with the engine off ?

Basjoos has his fuel /speed number on the forum somewhere - I think in his aerocivic thread about dropping its cd to around 0.17 .

His figures were with steady state driving IIRC - using lean burn though.

I'm miserably bad at math, so please check my numbers .

.31 Cd minus 45% equals .1705
45 MPG plus 110 % equals 94.5 MPG

So a reduction of 45% in drag equals a 110% increase in fuel economy ?