14 hours ago
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Fuel is expensive right now. But you already knew that.
Did you know, however, that having under-inflated tyres can make your car less fuel-efficient?
According to the RACV, when your tyres are under-inflated, they create more 'rolling resistance', meaning you need to accelerate more, which puts pressure on your engine and makes it consume more petrol than it should.
"For every 1psi drop in tyre pressure, fuel efficiency can decrease by up to 0.3 per cent, leading to higher fuel costs over time," the RACV website states.
Fortunately, there is a sticker inside your car called a 'tyre placard', which will tell you the recommended tyre pressure for your car.
The measurement for tyre pressure most commonly used in Australia is called PSI, which stands for 'pounds per square inch' (yes, sometimes the imperial system prevails – even in Australia).
There is a metric unit of measurement called a kilopascal (kPa). It's less common at service station air compressors, which usually default to PSI, but if your tyre placard uses this measurement, divide the kPa by approximately 6.9 to get the PSI.
For daily driving, recommended PSI levels usually sit between 30 and 40psi, but certain cars and conditions fall outside of these parameters.
How much should you inflate your tyres?
The advised inflation level of your tyres varies depending on a few factors, including the size of your car, how many passengers you are carrying, and whether you are transporting any heavy loads.
Your car should have a sticker somewhere – usually on the inside of the driver's side door, but otherwise inside the fuel cover flap or in the glovebox – stating your car's recommended tyre pressure.
If you don't have a sticker, try your car's manual. If still no luck, here is a rough guide, according to the RACV.
Many relatively modern cars will yell at you if any of your tyres are low on air, but if you have an older ride, it may not give you a courtesy 'beep' to warn a tyre has run out of the recommended amount of puff.
If you don't have a tyre pressure gauge at home, you can use the one at your local servo, which is also usually an air compressor.
"Always check the pressure when the tyres are cold, as heat can cause a temporary rise in pressure resulting in an inaccurate reading," the RACV site states.
If your only option is a service station gauge and compressor, the NMRA advises to factor in an extra 2psi to the recommendation "to account for the increase in temperature and pressure".
You can also buy home gauges and air compressors – making the whole 'cold tyre' thing more practical.
The NMRA recommends checking your tyre pressure every week or so, or at least every time you refuel, as incorrect tyre pressure can not only affect your car's fuel consumption but also its safety.
Under-inflated tyres can cause reduced traction, longer braking distances and poor cornering ability, while over-inflated tyres can decrease grip on the road and cause uneven tyre wear.
It's also important to check the pressure of your spare tyre – which sometimes has a different recommended PSI to your regular tyres, depending on its size.
Jemimah is Drive's Consumer Editor. She has more than a decade of editorial experience and has previously worked in property and lifestyle journalism for Domain, The Age, The Sydney Morning Herald and REA Group, among many other publications.
