Nitrogen vs Normal Air in Tyres - Is It Worth Paying For?
A practical guide to nitrogen in tyres for UK drivers, from the CarPal mobile tyre team.
What the claim is
Nitrogen is sold on the basis that its molecules are larger than oxygen molecules, so it escapes through the tyre wall more slowly and keeps pressure stable for longer. It is also dry, so there is no moisture inside the tyre to expand with heat or corrode the rim.
All of that is technically true. The question is whether it matters for a normal car on normal roads.
What it actually delivers
Normal air is already about 78% nitrogen. Filling with pure nitrogen takes you from 78% to around 95%, which is a smaller change than the marketing implies.
Pressure loss does slow slightly. In practice you might go from losing 2 PSI a month to losing a little over 1. That is a real difference but not one that removes the need to check your pressures.
The moisture argument is more relevant in motorsport and aviation, where tyres get far hotter than anything you will achieve on a commute.
The practical downside
Once you have nitrogen, topping up means finding somewhere that offers it. If you top up with normal air — which you absolutely can, safely — you dilute the nitrogen and lose the marginal benefit you paid for.
A correctly inflated tyre on normal air outperforms an under-inflated tyre on nitrogen every single time. Checking monthly matters far more than what the tyre is filled with.
The verdict
If it comes free with your tyres, take it. If you are being asked to pay for it on a road car, the honest answer is that the money is better spent on a decent tyre or a good pressure gauge.
And yes, you can mix nitrogen and air without any problem at all.
Frequently asked questions
Is nitrogen in tyres worth it?
On a normal road car, the benefit is marginal. If it is free, take it. Paying extra is hard to justify.
Can I put normal air in nitrogen-filled tyres?
Yes, completely safely. You simply dilute the nitrogen concentration.
Does nitrogen stop tyres losing pressure?
No. It slows loss slightly — you still need to check monthly.
Is normal air mostly nitrogen anyway?
Yes, around 78%. Nitrogen filling takes that to roughly 95%.
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