okay, maxed tire pressure doesn't help mpg like i originally thought, but...
 

does add about 10mph on max speed ;). but back to my thread's topic, i was believing this without ever trying to experiment and had my tires basically maxed out until today and noticed better mileage with pressures 11 lbs under max. i can only assume the tires grip better with the extra rubber on the road and doesn't make the engine work as hard.

Crazy interesting! I assumed as well that good tire pressure promoted better gas mileage since I 'believe' I saw improvement in my SUV after filling up the tires....although could also be driving style in the same respect. Ie: being heavier or lighter, hwy or city or interstate, towing or not. Anyway, sounds like a real good project for myth busters!!

yea i don't really get it. it's an s5 na, the auxiliary port for rotor #1 is not functioning since i broke the shaft which connects to the actuator and if it was than that alone would probably add mpg and a little performance. for a fact the higher tire pressure does make the car go faster, idk about acceleration.

More tire on the road means more friction, more friction means more power to overcome friction, means worse gas mileage.

The fact that you learned that you can go 10 MPH faster with the extra inflated tires means your MPG experiment is pretty moot.

That is completely backwards. If you want to minimize rolling resistance you use super skinny tires. Look at street bicycles.