Bibendum:
Check this info. out from Tirerack:
http://www.tirerack.com/tires/tiretech/pressure.htm
Why do you have to go to a gas station to check your tires? Just check them at home in the morning before you move the car. As far as the problem of air pressure increasing, I go to the gas station at night, I put extra air in the tires at the gas station, then drive slowly back home and park the car for the night. The next morning, I bleed the tire pressure down to the desired psi. In winter, I lock the car and keep the garage door open during that night, and in the morning I can bleed the tires and not worry about the heat in the garage affecting the air pressure and giving an inflated reading.