Nitrogen vs Air in Your Tyres: Is It Worth Paying For?
Many tyre shops offer to fill your tyres with nitrogen instead of ordinary air, often for an extra fee. It sounds impressive, but is it worth paying for? For most drivers the answer is no, or at least not as a priority.
Short version: ordinary air is already about 78 percent nitrogen. Filling with pure nitrogen gives small benefits, but it does not replace checking your tyre pressure every month.
What is in normal air?
The air around us is roughly 78 percent nitrogen and 21 percent oxygen, with small amounts of other gases and some water vapour. When a shop fills your tyres with nitrogen, it removes most of the oxygen and moisture. The tyre ends up with something like 90 to 99 percent nitrogen, depending on the equipment and how well the tyre was purged.
The claimed benefits
Slower pressure loss
Nitrogen molecules are slightly bigger than oxygen molecules, so they pass through rubber a little more slowly. In tests, nitrogen-filled tyres lose pressure somewhat more slowly than air-filled ones, but the difference is small. Tyres still lose pressure over time, and they also leak through the valve and where the tyre meets the rim.
Less moisture inside
Dry nitrogen contains almost no water vapour. Moisture in a tyre can make the pressure change more as it heats up and cools down, and in theory it can encourage corrosion of steel wheels. For ordinary road driving the effect is minor.
Less oxidation of the rubber
Oxygen slowly ages rubber from the inside. With less oxygen, ageing should be slower. Again, the real-world difference on a car tyre is usually small compared with the effects of heat, sunlight, load and time.
More stable pressure
This is why racing teams and aircraft use nitrogen. When the pressure has to be exact and consistent in extreme conditions, dry nitrogen helps. Everyday driving is different.
What nitrogen does not do
- It does not stop leaks from punctures, valves or rims.
- It does not make tyres immune to pressure changes as the weather warms and cools.
- It does not remove the need to check pressures regularly. See correct tyre pressure in hot weather.
Can I mix nitrogen and air?
Yes. Topping up a nitrogen-filled tyre with ordinary air is safe. You just dilute the nitrogen, and you lose some of the benefit. If you often top up at a station that only has air, nitrogen filling is not worth the cost.
Is it worth the price?
It can be reasonable if:
- The shop offers it free or at a small charge when you fit new tyres.
- You are able to return regularly for nitrogen top-ups.
- You want the most stable pressures for a car that sits or is used rarely.
It is usually not worth a large extra fee. The same money is better spent on a good pressure gauge, an alignment check or quality tyres.
What matters more
- Check pressure monthly, when the tyres are cold.
- Set the pressure to the figure on your car's placard.
- Check the spare too.
- Look over the tyres for cuts, bulges and uneven wear. See signs you need new tyres.
Whether you use air or nitrogen, a correctly inflated tyre is what keeps you safe and saves you money.