Actually you're filling up with mostly N, not O, regardless of where you go. Air is 78% Nitrogen, 21% Oxygen so pure Nitrogen isn't gaining you very much. Racers use it because even 1/4 lb of pressure makes a difference in handling. The biggest benefit of pure Nitrogen isn't the smaller pressure change, it's the fact that it's drier so you have less moisture inside the tire which helps resist rust long term. Might also help with the new pressure sensors.