[Emoto]

Just a minor point: Fuel economy improves with more air pressure in the tires not so much because of contact patch size, but because of decreased rolling resistance. With higher PSI, the tire is less flexible, so that flex needn't be overcome when rolling.

Another point is that the lower the tire pressure, the more the tire will flex. The more it flexes, the more heat will go into the tire. The "right" amount of flex will give you more grip due to the tire compound being up to temp (to a point). Not enough flex impedes traction because the tire stays cold(er) and the tread compound doesn't flex against the pavement imperfections as well.

The PSI spec on the door sticker should be a good compromise of all factors. I will typically run a little higher just for a little more economy on vehicles like my Jeep.

An overinflated tire will wear out the center of the tread first. An underinflated tire wears out both edges first.