Tyre Pressure and Fuel Economy: How Much You’re Actually Losing
Of all the ways to trim your fuel bill, checking tyre pressure is the one that costs nothing and takes five minutes. Yet soft tyres are everywhere, quietly adding to the cost of every kilometre. This guide puts real numbers on what under-inflation costs at the bowser, explains why it happens, and clears up the myth that more pressure always means better economy.
Why do under-inflated tyres use more fuel?
It comes down to rolling resistance — the energy your engine spends just to keep the tyres turning. A soft tyre flattens out more where it meets the road, flexes harder and deforms more with every rotation. That flexing turns fuel into heat instead of forward motion. Michelin notes that rolling resistance accounts for a meaningful share of a car’s fuel consumption, so anything that increases it — and low pressure is the biggest culprit — shows up directly at the pump. The same soft tyre is also running hotter and wearing on both shoulders, so you lose money twice: once on fuel, once on tyre life.
How much fuel does low pressure actually cost?
The most-cited figure, from a US NHTSA study and quoted by Australian retailer Tyrepower, is that every 1% drop in tyre pressure correlates to roughly a 0.3% reduction in fuel economy. That scales up fast on tyres that are properly soft:
| How under-inflated | Approx. extra fuel used | Real-world example |
|---|---|---|
| 10% low (e.g. 32 → 29 psi) | ~2% more fuel | Easy to reach in a month of no checks |
| 20% low (e.g. 32 → 26 psi) | ~4% more fuel | A visibly soft tyre |
| 40% low (e.g. 32 → 19 psi) | ~8% more fuel | Dangerously low — blowout risk |
On a car using 8 litres per 100 km, a steady 4% penalty is roughly an extra 0.3 L/100 km — real money over a year, and it does nothing but cost you. These are guide figures; the exact saving depends on your car, tyres and driving. But the direction is never in doubt: soft tyres always cost fuel.
Does over-inflation improve fuel economy?
Barely, and it isn’t worth it. It’s true that a harder tyre has marginally lower rolling resistance, which is why the myth persists that pumping tyres up saves fuel. Tyrepower is blunt about it: “There is a myth that the more your tyre is inflated, the better fuel economy is. This isn’t true.” Over-inflation shrinks the contact patch, so you trade a tiny fuel gain for centre wear, a harsher ride, longer braking distances and worse grip in the wet. The economy sweet spot is simply your placard pressure — no more, no less.
What pressure gives the best economy?
Your car’s placard figure. It’s set by the manufacturer to balance economy, grip, wear and comfort. Follow the placard, not the sidewall maximum, and check the tyres cold. Because pressure naturally leaks and drops with temperature, the only way to stay at the economy sweet spot is to check regularly — see how often you should check tyre pressures. Monthly, plus before long trips, keeps you close to optimal all year.
What else affects tyre-related fuel use?
Pressure is the biggest lever, but not the only one. The tyre itself matters: low-rolling-resistance tyres carry a better fuel rating on the tyre label — learn to read it in how to read a tyre label’s fuel and wet grip ratings, and see our pick of fuel-efficient tyres for a hatchback. Weight matters too — a loaded car and a heavy EV both need higher pressures to stay efficient, which is why EVs often run higher placard pressures. And no, nitrogen fill won’t save you fuel; only correct pressure does.
Frequently asked questions
How much can correct tyre pressure really save me?
Tyres running 20% low waste around 4% more fuel. Correcting them costs nothing and takes minutes, making it the cheapest fuel saving available to any driver.
Should I over-inflate my tyres to save fuel?
No. The fuel gain is tiny and you lose grip, ride comfort and braking, and wear out the centre of the tread early. Stick to the placard pressure.
Why do my tyres lose pressure over time?
Tyres slowly permeate air through the rubber, and cold weather lowers pressure too — roughly 1 psi for every 5–6°C drop. That’s why regular checks matter for economy and safety.
Do fuel-efficient tyres make a bigger difference than pressure?
They help, but correct pressure comes first — a fuel-saving tyre run soft loses its advantage. Get the pressure right, then choose a tyre with a good fuel rating on the label.
Figures here are general guides for 2026 and vary by vehicle and tyre. Confirm your correct pressures on your placard. Authority sources: Tyrepower — how tyre pressure affects fuel economy and Michelin Australia — rolling resistance.
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