posted on May, 9 2009 @ 02:43 PM
I'm surprised that people are so insistent on driving at speeds lower than the speed limit. Every car is geared differently, and speed limit vary by
state, highway, region, etc. I have a 2005 Grand Prix GTP (Supercharged), and I get my best mileage at 71 mph on cruise. My highway mileage is usually
about 24 mpg, but with minimal traffic, I can easily pull 25 mpg at 71 mph, with the tach at about 1800 rpms. I suggest finding a comfortable speed
where the engine is running at low rpms. That's where you will get your best mileage.
And as far as running your tires at 40-45 psi is concerned, your tire generate heat and build up pressure quite easily. For example, in dirt track
racing, we sand our tires to remove the glaze after each race, and sipe them (adding cuts so they heat up faster). When we sand them, we can up the
pressure 2-3 psi easily. That's a light sanding, without generating nearly as much heat as you would on a 95 degree day on an asphalt road.
I also work on semi-trailers for a living. A common 22.5 tire is filled to 95 psi, and that pressure can double under load when it gets hot.
By over pressuring your tires, you'll reduce the longevity, and risk exposing any flaws in the tire when it heats up, potentially exploding the tire.
Blow a low-profile tire, you can damage the rim, blow a high-profile tire, especially a steer tire, and you can find your self fighting to control