I thought the nitrogen filled tires didn't loose or gain pressure due to cold or warm weather/tires??? That would be the reason to use the nitrogen.. Anyway, 2 weeks ago when the cold snap hit here in AL, mine (all 4) got to around 29 psi and no light came on, I just double checked them with my tire gauge and filled them all back up to 36 psi.. I was pondering the idea of geting nitrogen put in but it sounds like this doesn't really help or they charged you for the nitrogen and put in air?.... who knows..