The auto manufacturers are pulling out all the stops to increase gas mileage, because they know higher mileage sells cars. They are spending big bucks to drill lightening holes in various components to save an ounce or two. All so that, on test day, the car might squeak out one more MPG. Given all this, and the known benefit to gas mileage of the relatively simple and no-cost step of increasing tire pressure, isn't it logical to assume that the max tire pressure listed on the doorframe/owners manual is really the maximum safe pressure to which you should fill the tires? On test day, the tires can only be inflated to the max PSI recommended in the manual. The max pressure listed on the sidewall is not the right number to use.