Whenever I fill my tires, I always use an 80% nitrogen mix, Its been working for me for years.
NOTE - the air you breath is 80% nitrogen, the compressor at the gas station will do just fine, it also is 80%.
Why I use 1100% nitrogen in my airplane tires:
1) We use a high pressure nitrogen bottle (3000 psi) when we service our tires to as much as 250 psi. Most standard compressors will not get to the pressure we need in our tires, and are horribly inconvenient to haul around to check and add air to tires.
2) Gas station compressors don't dry the air. The nitrogen in the tank is waterless, and has been dried, thus eliminating the possibility of water condensing and freezing inside the tire. Unless you drive your car at 40,000 ft with an outside air temperature of -65 degrees, this will probably not be an issue.
3) Autoignition - When a 250 psi tire reaches a temperature of approximately 500 Deg F, There is a possibility of the tire exploding if it has an oxygen source internal (not filled with 100% Nitrogen). The FAA has tested this and has issued an directive to use 100% nitrogen.
4) At the high pressure, nitrogen is molecularity larger than an oxygen molecule, and can reduce minor losses of tire pressure and minor degradation of tire rubber due to oxygen impregnating the rubbers used in tires. (very minor issue, but is more of an impact with high pressure tires (450 psi)
Its important to note that item #4 isn't the reason Nitrogen is used in airplane tires, but is a small side effect of using nitrogen in aircraft tires.
The main reason is items #1 and to a lesser degree, #2. #3 is somewhat irrelevant, as at 500 Deg, the tire is on fire.
I suspect if I took two aircraft tires inflated to 250 psi, one was inflated with shop air and the other out of a nitrogen tank. You could set them on the ramp for ten years, and when you come back, you'd see the one with shop air lost a couple psi more than the one with 100 % nitrogen.
Would I use nitrogen in my car tires? No, the extremely small benefits for car tires isn't worth the addition work or cost.