Nitrogen-filled car tyres

An industry promotion which raises its head occasionally centres around the so-called benefits of having car tyres filled with nitrogen. Wondrous claims are often made that are either mis-leading or simply plain wrong.

The comments below are taken from a recent email we received which is worth posting.


Claimed benefits and our comments

Reduce tyre wear by up to 50%
Correct tyre inflation is the main factor with tyre wear, not what you inflate the tyre with.

Nitrogen molecules are bigger than oxygen molecules, and hence your tyres will leak less
Motorists pump "atmospheric air" into their cars tyres normally, which consists of 79% nitrogen. Consumer Magazine did a 12 month test of this, and had trouble measuring the difference between the two it was so small.

Nitrogen will improve the car's ride
Nitrogen and "atmospheric air" have almost exactly the same compressibility, since atmospheric air is 79% percent nitrogen.

Nitrogen will improve the car's fuel economy
Correct tyre inflation (and regular checking) will have the bigger impact on fuel economy. As will the use of your right foot.

Nitrogen will reduce tyre rot and corrosion
Take a look at the outside of any car tyre, which is continuously exposed to "atmospheric air" and you won't observe tyre rot.


A previous AA "Ask Jack" answer and Consumer report on nitrogen in car tyres supports the above.

Nitrogen is used in places like air plane tyres and fire truck tyres because of the reduced risk of fire. Nitrogen is also used when tyres are exposed to extreme heating, because it doesn't heat as much when placed under pressure when compared to "atmospheric air".

Imagine the sudden load an airplane tyre experiences when landing. Some heavy trucks also use nitrogen to reduce tyre wear caused by having a heavy load causing excess tyre heating. Racers who use proper race tyres designed to operate at high temperature use nitrogen because nitrogen makes the tyre run cooler and last longer.

Note: The AA recommends motorists check their tyre pressures at least monthly and especially when they plan to carry heavy loads or go on long trips.  You can do this for free at any service station (its best to do this when tyres are cold), and recommended tyre pressures are usually printed on a label in the driver's door pillar or in the owner's manual.

Regularly topping up tyres would be difficult if owners used pure nitrogen which is not available at service stations.