How do I check my car's tyres and oil?

Under-inflated tyres and low oil are behind a large share of breakdowns, poor fuel economy and MOT failures. Both are checkable in minutes with no tools, and both are things garages find surprisingly often on cars brought in for something else.

Safety

What you'll need

• Tyre pressure gauge or forecourt airline
• Kitchen roll or cloth
• A 20p coin (optional)
• The handbook (optional)

Step by step

1. Find the correct tyre pressures for your car.Inside the driver's door frame, the fuel filler flap, or the handbook. Front and rear often differ, and there is usually a higher figure for a fully loaded car.
2. Check pressures when the tyres are cold.Before driving, or after less than a couple of miles. Driving heats the air and raises the reading, which makes a hot check misleadingly high.
3. Check all four tyres and the spare.The spare is routinely forgotten and routinely flat when needed. If you have a repair kit rather than a spare, check its sealant expiry date.
4. Check tread depth with a 20p coin.Insert it into the tread grooves. If the outer band is visible, the tread may be below the legal minimum and needs measuring properly.
5. Look at the tyre condition as well as the depth.Cuts, bulges, cracking in the sidewall, and uneven wear. A bulge in a sidewall means the tyre must be replaced immediately.
6. Check the oil on level ground with the engine off.Wait at least ten minutes after running so the oil drains back down. On a slope you get a false reading.
7. Pull the dipstick, wipe it, reinsert fully, and pull it again.The first reading is meaningless because oil splashes on the way out. The second reading is the real one.
8. Top up in small amounts if it is below the minimum mark.Add a little, wait a minute, recheck. Overfilling is genuinely damaging and harder to fix than underfilling.

Tips

• Uneven tyre wear tells you something: wear on both edges means under-inflation, wear in the centre means over-inflation, and wear on one edge suggests alignment.
• Check the oil level before a long journey as well as monthly. A car that uses oil between services will use more on a motorway run.
• Check screenwash, coolant level and lights at the same time. It turns five separate jobs into one monthly routine.

Common mistakes

• Checking tyre pressures after a long drive — Heat raises the pressure reading, so you let air out of correctly-inflated tyres and end up under-inflated when cold.
• Reading the dipstick the first time it comes out — Oil splashes up the stick while the engine runs. Only the second reading, after wiping and reinserting, is accurate.
• Overfilling the oil — Too much oil can cause foaming and seal damage. It is a more serious problem than being slightly low.

Questions people ask