I recently had new tires installed and decided to have them filled with Nitrogen instead of air and they seem to pretty much stay consistant at 36 psi but will drop to 33 with extreme cold. Yes I live in Alabama, but I travel all over, even up north..lol. just my 2 cents. They claim the Nitrogen helps the tires last longer,,, hmmm we shall see.. I think it usually costs about $7 per tire to do this, but my tire store didn't charge me.