i drove for a while with over inflated tires (not intentionally
) ..it made the car wander on the freeway at higher speeds, understeer in the rain
and twitchy round bends even when dry. I was glad to get the correct pressure in those fronts, i can tell ya. The best way to improve MPG is to be smooth and anticipate the traffic ahead. For the V6 guys, shift before the secondaries open..G.