My dream P has 21” tires and even with nitrogen the tire pressure increases with driving time. I suspect that tire friction/ heat increases with driving time.
In addition I am not trying to make converts out of anyone but stating actual physical difference that I experienced in New England where temperature can fluctuate with a delta of +-40degrees at any given time in the winter.
The density of nitrogen is 1.251 versus 1.225 for air at sea level 15 degrees C or 59 degrees F. Thus the net affect would be the same regardless of temperature
I respectfully disagree. If you go from 2.1 to 3.0 in mileage at 17 Fahrenheit that is a significant difference. That coupled with no moisture has made a believer out of me.
Unscrew the the valve pin it will let all the air out and deflate the tire completely. Then screw valve pin back in and fill with nitrogen. Rather simple process. Make sure tires are cold and refill to 45 psi when cold.
I just purged all the air out of the tires and replaced it with nitrogen. Marked mileage difference even in extreme cold (17degrees) get up to 3.0 m/KWm. Recommend this to all owners.