[200q20v] Re: [V8] V8 and 200q20v difference

[Michael L. Riebs]

> Nowadays, the
> biggest tire-related variable for fuel economy is certainly inflation
> pressure . This affects both the radius *and* rolling resistance,
> which IMO might account for a several mpg effect.

This is definitely correct! I recently drove a Chevy ½-ton PU for an
extended period of time, and it had a front-tire slow leak. I was closely
monitoring fuel economy, in an attempt to determine budgets for our business
for the future purchase of one of these beasts (I can inform that a Chevy
Silverado has about 3 mpg better economy than a similar Dodge Ram).

The first few tanks gave me a reading of about 15.7 mpg, but suddenly I was
getting only high 12's. I tried to drive with the proverbial "rotten egg"
under my foot, but to no avail. I then had the left front inflated properly,
and immediately the mileage was back where it had been.

The observation about the hardness of the tire compound is founded on the
same principals - higher rolling resistance - lower mpg, and vice-versa. And
there are still differences in the commercially available compounds - albeit
not as significant as, say, in F-1 racing. Take for instance the Discount
Tire 4-wheel special for $100 with the 70K mile warranty. How do you think
those tires rate, next to say, Pirelli P-55's, that, if driven carefully,
*might* last 35K? Not to mention the handling - but that's another thread.

Michael Riebs
Grand Rapids, MI
'90 V8Q
'98 A6QA