Keeping your tire pressure (psi) at the correct level will mean that you avoid wasting fuel. If a tire is under-inflated, it will not roll as efficiently as a tire at the correct pressure and this will reduce your fuel mileage.
A recent survey by the Kwik-Fit Group in the UK showed that around 68 per cent of cars in the country had under-inflated tires – at least 3psi under the manufacturer’s recommendation – and that this was costing motorists almost £1 billion a year in extra fuel. Meanwhile, in the US, a survey once showed that as many as 85 per cent of motorists did not properly check tire pressures.
Figures from the US government show that if you keep your tires at the recommended pressure, you will save around 3.3 per cent on your fuel costs. Studies have shown that under-inflated tires can lead to a reduction in your fuel mileage of around 0.3 to 0.4 per cent for every 1psi drop in the pressure of your vehicle’s tires.
You can check the required pressure for your tires in your owner’s manual. The pressure should also be shown on a sticker on the vehicle – usually on a door jamb or in the glove box. Do not rely on the maximum pressure figure found on the sidewall of a tire because it does not indicate the correct pressure for your vehicle’s tires. If you over-fill a tire that can lead to irregular wear and, possibly, bulging of the sidewall. However, bear in mind that the pressure may need to be increased if you are planning a lot of high-speed driving or if you are placing a heavy load in your vehicle.
Visually check your tires each day to make sure they are not looking under-inflated and check the pressures with a tire pressure gauge at regular intervals – say, once a month. Top up the tires with air, as required. Check the pressure when the tires are cold because you could get a misleading reading if the tires are warm since temperature can alter the pressure in a tire. Altitude can also affect tire pressure, so bear this in mind if you are traveling in a mountainous area.
Keeping your tires at the correct pressure will not only help your fuel mileage, it will also stop your tires from wearing out more quickly and it will help to ensure that your vehicle handles properly. Tread damage and blow-outs can be caused by under-inflated tires.