Does filling tyres with pure nitrogen give better performance and fuel economy?

This is a question that has been asked many times over the years.

The short answer is: Yes, it does.

But the answer is slightly complicated as many factors can affect the characteristics mentioned.

By and large, the benefits nitrogen has over plain air from petrol stations or auto workshops are marginal in day-to-day applications but may be exploited in certain applications such as in aviation and motor racing.

As earth's atmosphere is already made up of 78% nitrogen with the remainder being oxygen (21%) and of all other gases (1%), the only parts that can make a difference accounts for less than one quarter.

Some points raised in favour of inflating tyres with pure nitrogen are indeed indisputable.

For instance, the molecular size of nitrogen is bigger versus oxygen (0.305 versus 0.299 nanometers), this means it is harder for it to escape thus giving your tyres a more constant pressure over time.

US consumer watchdog, Consumer Reports, conducted a test on pressure loss between both gases and found that there was only a 1.3psi (0.089 bar) difference between the two over a period of one year.

Another point is that oxygen affects the tyre’s pressure and performance when heated, however, a tyre filled with nitrogen will also heat up but to a marginally lesser degree.

The benefits of using nitrogen in tyres can be proven in lab conditions but such gains can be difficult to quantify meaningfully in day-to-day use, bearing in mind that the purity of hydrogen inflated into the tyres also plays a role.

Meanwhile, other real-life factors also can also play into loss of pressure like tyre fitting on the rim, valve and measuring equipment tolerances so the best way is to always check your tyres regularly. — C.Y. Lee