Cars aged 15 and over: the MOT fails that arrive with age, and what to check

The short answer

Cars aged 15 and over fail the MOT more often than any younger group, and they fail on different things. In tests carried out 2021 to 2025, about 4 in 10 first tests on cars aged 15 (42.4% of 6,856,204 tests) ended in a fail or a pass after a fix on the day. The pass rate at age 15 was 57.6%, against 58.9% at 14 and 56.0% at 17.

The items that mark this age out are the ones a tester finds underneath and behind the car: corroded brake pipes, corroded suspension mountings, exhaust leaks, lamps that have stopped working and headlamps pointing the wrong way. Tyres and brake pads, the fails that dominate younger cars, barely move between 10-14 and 15 and over. So the checks for a very old car are different checks, and most of them need the car on a ramp or in the dark.

What the data shows

The table gives the share of all first tests in each age band that recorded the item as a fail. Age is the test year minus the first-used year. The items were chosen because they rise sharply, or appear for the first time, in the oldest band.

Two things stand out. First, the corrosion items are close to zero or below the reporting floor until 10-14, then jump: corroded suspension mountings go from 0.3% to 2.2% of tests, corroded brake pipes from 0.8% to 2.1%. Second, the everyday wear items level off. Tyre tread below the limit was recorded in 2.9% of tests at 15 and over against 3.0% at 10-14; brake pads worn under 1.5 mm in 1.8% against 2.1%. Owners of very old cars seem to keep up with tyres and pads. What they cannot see is what gets them.

Lamps are the single biggest group. A position lamp (a side or tail light) not working was recorded in 5.4% of tests at 15 and over, a stop lamp in 3.8%, and headlamp aim that was obviously wrong in 3.3%. Wipers that did not clear the screen were recorded in 3.1%.

Why these items and not others

The data records what the tester found, not why. But the pattern fits what age does to a car in a wet, salted climate. Steel brake pipes and the body around suspension mountings rust from the outside, slowly, and a tester with a hammer and a lamp is often the first person to look. Exhaust systems rust through from the inside. Rubber perishes, so bulb holders corrode and lamp earths fail. Headlamp aim drifts as suspension sags and as lamps are replaced.

The emissions item is a lambda reading outside the limit after the second fast idle, which is a catalyst or sensor past its best. The airbag warning lamp is an electrical fault in a system the car cannot be tested without. Both are rare on younger cars and both climb steadily.

Two heavier structural items also appear only at this age: the seat belt mounting area with its strength reduced (0.9% of tests at 15 and over) and the integral structure corroded so that rigidity is reduced (0.6%). Those are the fails that end a car's life, and they are not visible from the driver's seat.

What to check on a car aged 15 or more

1. History first. Read every test on the GOV.UK MOT history service. Look for corrosion advisories that repeat year after year on brake pipes, subframes, sills or suspension mountings; a fail on any of those in a past year tells you where to look now.
2. Lights, all of them. With a helper, check every side light, tail light, brake light, number plate lamp and indicator. These are the cheapest fails on the list and the most common.
3. Headlamp aim. Park facing a wall at dusk. Two beams at clearly different heights, or one pointing at the sky, is the item in the table.
4. Underneath. If you can, look along the brake pipes for flaking rust and at the suspension mounting points on the body for bubbling or holes. A garage ramp inspection before buying is worth the price on a car this age.
5. Exhaust. Listen for a blow at idle and run a hand (engine cold) along the joints for soot.
6. Warning lamps. Turn the key and watch the airbag and engine lamps go out. One that stays on is a fail before the test starts.
7. Tyres and pads still matter. They are just not what sets this age apart.

If the car is yours and the test is due, the GOV.UK guide to getting an MOT explains the timing and the retest rules.

What this does not mean

These are national shares across tens of millions of tests. They say how often each item was recorded on cars of each age, not what will happen to any one car. A 16-year-old car that has lived in a dry garage and been undersealed can be cleaner underneath than a six-year-old that has done winters on gritted roads. The figures tell you where to look; they do not tell you what you will find. And a pass at 15 is not proof of a sound car: it means nothing on the day was bad enough to fail.

Sources and method

Shares are national: first tests in each age band (test year minus first-used year) that recorded the item as a FAIL, divided by all first tests in the band, test years 2021 to 2025 pooled. Bands hold 33,793,352 (aged 3-5), 50,103,915 (6-9), 44,980,002 (10-14) and 31,405,150 (15+) first tests. The age-15 pass and fail rates in the opening are from the national roll-up by single year of age: 6,856,204 first tests at age 15. 'Below floor' means fewer than 20 tests recorded the item in that band, or the item did not appear in the band's top twelve. Items are the DVSA reasons for rejection, shortened; where DVSA lists the same item under two wordings only the wording shown is counted.

• DVSA anonymised MOT results, class 4 first tests, 2021-2025
• GOV.UK: Check the MOT history of a vehicle
• GOV.UK: Getting an MOT

This article is general information drawn from published test records. It is not professional, mechanical or legal advice, and an MOT pass or a clean MOT history does not guarantee that a car is roadworthy today. If you are unsure about a car, have it inspected by a qualified mechanic. You can check any vehicle's MOT history free on the official GOV.UK MOT history service.