What are the benefits of filling nitrogen gas in automobile tyres?

1. Air contains oxygen, nitrogen and other gases. Oxygen helps flames to extend. That is why we see when there is a heavy wind flame will spread at a faster rate and extinguishing the fire is difficult. Pure nitrogen will not have any oxygen content in it and nitrogen is almost treated as an inert gas. So by any chance, if there are any sparks nitrogen will see that they will die down.
2. Normal air contains around 78% nitrogen and 21% oxygen. There may be some other impurities including some moisture in it. This moisture may start getting vaporised at higher temperatures and may cause high pressure in the tyre. This is never a desired condition.
3. The reactivity of oxygen with rubber may lead to leakage and may cause inflation. But nitrogen is very slowly passing through the rubber and hence chances of leakage are very less when compared to that of air.
4. Tyres with less inside pressure are not good for your health and your hip pocket. A tyre having incorrect pressure will have less grip. So it will become very difficult to control the car. We can't say that nitrogen will not leak but the rate is less and the frequency of filling gas in the tyre will come down. This is mainly because the molecule size of nitrogen is higher than that of oxygen.
5. As nitrogen is not very reactive rusting of metallic parts will be prevented,
6. Nitrogen acts as a coolant and hence the tyre temperatures will not enhance easily
The above are some of the advantages.

The air which we fill in the car tyre contains about 20% Oxygen. This Oxygen is actually not required basically due to safety reasons and it can help in rubber burning in some adverse conditions.
Further the leaking rate of Oxygen is more than that of Nitrogen and if logistically possible it would be better to have only Nitrogen gas in the tyres.
Practically speaking, air is a far cheaper medium as compared to Nitrogen so it is used everywhere.

The following are the advantages of filling Nitrogen Gas in the automobile tyres -
1) Nitrogen filled tyres would eliminate the water vapour molecules which otherwise could have entered in airfield tyres. This would not allow of occurrence of fluctuation of tyre pressure in case of usage of Nitrogen gas.
2) Nitrogen gas produces coolant effect within the tyres as compared to the usage of compressed air.
3) Since Nitrogen Gas takes care of temperature with less surging of temperatures within the tyre, it might be treated as the ideal substitute. The compressed air lacks this characteristic.
4) Time to time, one has to ensure the correct tyre pressure in case of filling of air since its rate of escape is more than that of Nitrogen gas due to larger molecules of former one. The pressure of Nitrogen filled tyres remains constant for an appreciable time due to inherent characteristics of Nitrogen.