I stopped to check my air pressure and bump them up a couple psi. I checked them two weeks ago and set the new pressure at 42F and 40R. Today one R tire had dropped 4 psi and the other three were down around two psi each. Stay on top of your tire pressures for at least the fuel mileage aspect.
I am constantly checking tire pressure (this morning, in fact) and making certain I have no pressure loss. About three years ago I decided to pick up a portable air compressor that could be packed into my Prius. I found an inexpensive model that can be powered through the 12v socket in the car. You could use this to pump up a deflated spare or to help fill someone's low tire so that they could drive far enough to get to a service center without having to change a tire. This is particularly nice when it is late at night or bitterly cold or the driver happens to be elderly! Here is a link to a recent posting of mine about the portable compressor.
