**What\'s better? Lighter or more slippery?**

This is an interesting problem, and I am tempted to agree with Gern that it won't make any real difference. However, just to be a bit anal and *prove* it to myself, let's do the numbers... /images/graemlins/smirk.gif

Mk2 Golf/Jetta at 2300 lbs, a Cd of .35 and 20 sq ft of frontal area versus a Mk2 Scirocco at 2000 lbs, a Cd of .38 and what, ~16 sq ft (?).

For each, the combined (aero plus rolling drag) power required can be approximated as (8.702 x 10**(-6)) x Cd x A x V**3.

For the Golf at 60 MPH, that's (8.702 x 10**(-6)) x .35 x 20 x 60**3, or 0.000008702 x .35 x 20 x 216,000 = 13.2 hp.

For the Scirocco, that's (8.702 x 10**(-6)) x .38 x 16 x 60**3, or 0.000008702 x .38 x 16 x 216,000 = 11.4 hp.

Two hp at .4 lbs/hr/hp means the Golf will burn .8 lbs more fuel per hour than the Scirocco. Since diesel weighs about 7 lbs/gal, that is an extra tenth of a gallon of deisel an hour, or about 1 MPG.

As we thought, there isn't enough difference to clearly chose between the two. Drop the TDI into whichever car you wish and have a nut! /images/graemlins/grin.gif