I'm not a mileage fanatic, but like everyone else noted that my mileage suffers in the frigid (northern NJ) months (due to many factors).
I was driving to work the other day and my tire pressure gauge warning light lit up. The last time I ignored the light and went to Home Depot, it was flat when I got out, so I learned to not ignore this warning. I went to the gas station and three of my tires were at 29 psi and the rear left was 25 psi.
I was shocked to see how low it was.
I usually try to stay on top of the pressure in between rotations, but not as often during the winter.
In any event, I'm sure the low tire pressure contributed to the relatively poor winter mileage.
As every other car in the northern part of the country had to endure the same temperatures, I wonder how many others are driving with low pressure.

 

From Thermodynamic theory:

Pressure*Volume=k*Temperature(in absolute degrees - Kelvin or Rankin)

so if the temperature goes from 27 degrees C (A warm day, ~300 K) to zero C (A cool day, ~273 K) That is a 10% change in PSI (The volume is approximately constant).

JeffD

 

Your TPMS show a low tire?

 

On the flip side... If you add air to your tires in the winter to raise the pressure, you should check them again when it warms up in the spring. You might have to let some out to keep it below the limit.

I run mine at about 42 psi, checked on a moderate day. (Here in Florida, that's about 70 F, or 21 C.) Then, on a really hot day, it's still not over the limit that is printed on the sidewalls. And, on a really cold day (for here) it is still not too low.

 

Unfortunately, it's a guessing game, they narrow it down to one of the four tires. You get to crawl around and try to figure out which one it it.

It was a nail (in the 25 PSI) and the frigid temps (for the 29 PSIs)

 

Don't forget the spare tire!

I pulled mine out today and it was at 19 PSI.


Edit: The spare has never been out, never been used and still has the factory bar-code sticker on it.