Tyre Pressure and Fuel Economy: Check It Monthly

Tyre pressure is one of the cheapest and easiest ways to look after your fuel bill, and your safety.

Why tyre pressure affects fuel use

A tyre that is too soft flattens more where it meets the road. That increases rolling resistance, so the engine has to work harder to keep the car moving. Under-inflated tyres also wear faster, handle less well and can be dangerous at speed.

How much can it save?

The effect is usually modest, and it depends on how low the pressure is. But it costs nothing to fix. To put it in money terms: at 8,000 miles a year in a 40 mpg petrol car, you spend about £1,540 on fuel at today's prices. Even a 1% improvement is worth about £15 a year, and a 3% improvement about £46. Add the cost of tyres wearing out sooner and the case is clear.

Where to find the right pressure

Do not use the number printed on the tyre sidewall. That is the tyre's maximum, not the right pressure for your car. Instead look for:

• the handbook
• a sticker inside the driver's door frame
• the inside of the fuel flap

You will often see two figures, one for normal loads and one for a fully loaded car. Use the higher one when carrying heavy loads or on long motorway trips.

How to check tyre pressure

1. Check when the tyres are cold, meaning the car has not been driven, or only for a mile or two. Warm tyres read higher.
2. Remove the valve cap and press a pressure gauge on the valve.
3. Read the figure, in psi or bar, and compare with the recommended pressure.
4. Add air if needed. Most garages have an air machine, and many are free or cheap to use.
5. Refit the valve caps. Check the spare too if your car has one.

Many cars now have a tyre pressure monitoring system, but it only warns you when pressure has dropped a lot. Do not rely on it alone.

How often to check

At least once a month, and before a long journey. Tyres lose a little air naturally, and cold weather can lower the pressure further. See winter driving and fuel economy.

Other tyre tips

• Check the tread depth. The legal minimum in the UK is 1.6mm across the central three-quarters of the tyre.
• Look for cuts, bulges or uneven wear, and get them checked.
• Have your wheels aligned if the car pulls to one side.

Add it to your routine

Put a monthly reminder in your phone, and check your tyres when you fill up. While you are there, check what your local stations are charging and see more ways to save in 12 ways to cut your fuel bill.