Gas Mileage (was Re: GPS Car speed control advancing in UK)

From: James Rogers (
Date: Mon Jan 29 2001 - 12:01:50 MST

At 10:42 AM 1/29/2001 -0500, Michael Lorrey wrote:

>Some of the more efficient aerodynamic cars get better gas milage above
>highway speeds than at the '55 mph' standard hyped in the '70's. Heck my
>grandpa's old Tercel got 5 more mpg at 80 mph than at 55 mph.

My most recently acquired sedan has a computer that gives the instantaneous
gas mileage, and the results have been interesting. It is quite
aerodynamic and has a 270 HP engine. All the following numbers are on
straight level roads.

<40 MPH => 19 MPG
55 MPH => 22 MPG
70 MPH => 25 MPG
80-90 MPH => 27-29 MPG (optimal range)
100 MPH => 25 MPG
120 MPH => 20 MPG
(Engine is limited at 155 MPH, but even if I drove it that fast, I
certainly wouldn't be staring at the computer.)

The lowest I've ever gotten it is playing pole position on a long 7%
incline, which dropped it to the 10 MPG range +/- 2 MPG at a little under
red line (~ 6k RPM, it is an inline 6).

So yes, modern cars are frequently driven below their optimal speed. I get
something like 30% better gas mileage around my optimal range than the
posted speed limit in many locales. Therefore, I have an obligation to the
environment to speed. :^)

-James Rogers

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