Uh, never, ever fill with oxygen. Things like to spontaneously combust when exposed to a 100% oxygen environment.
Nitrogen is used because of it's inertness. That and the molecule (N2) is bigger than O and doesn't pass as easily through the rubber wall around it. Aircraft tires have been filled with nitrogen for, well, like ever. An aircraft tire goes from zero to 150+ mph in an instant during a landing evolution. Nitrogen is stable and able to take a beating from the heat that is generated. Wheel temps on the F18's I work on often hit 250*F and higher during braking. There's a plug in the wheel designed to melt at 450*F and deflate the tire in the event of a brake fire.