Tire Pressure Cost me!

[bronsin]

I check my tire pressures once a month. In the summer I seldom add air. But when temps drop in the fall I find that causes the pressure to drop maybe 5 psi. From like September to November. I use 35 psi. My mileage is pretty constant between 35-36 mpg. But when I checked my psi Nov 1st it was like 31psi all four tires. My mileage for that period is ~34. I added air just before the last fillup. When I checked it today it was 36 mpg. Im still waiting for the winter gas drop in mpg!