MOT data study
Which MOT advisories turn into a fail at the next MOT
DVSA MOT tests 2022–2025 · Updated
17.7% of MOT tests on vehicles aged 9 to 11 with a track rod end advisory were followed by a fail on it at the next MOT, against 1.9% without one (305,478 MOT tests with the advisory) [1].
- Brake pipes: 8.6% failed on them next time after an advisory, 23.3–23.8× the rate without one (0.37%).
- 47% of brake pipe advisories were given again at the next MOT, and 48% had nothing recorded.
- 29 parts show the same pattern in at least three of five age bands, each with a 95% interval, from 83,372,892 pairs of consecutive MOT tests, 2022 to 2025.
The parts most likely to fail after an advisory
29 MOT advisories ranked by how often they become a fail
Vehicles aged 9 to 11 at the first of two MOTs a year apart. "Failed next MOT" is the share whose next MOT failed on the same part; "No advisory" is the share of vehicles the same ages with nothing recorded on that part that failed on it [1].
| # | Advisory on | Failed next MOT | No advisory | Ratio | MOT tests with the advisory |
|---|---|---|---|---|---|
| 1 | Track rod ends | 17.7% | 1.90% | 9.2–9.4× | 305,478 |
| 2 | Drive shafts | 13.7% | 1.45% | 9.3–9.6× | 177,087 |
| 3 | Suspension arms | 11.9% | 3.62% | 3.3× (3.26–3.30×) | 1,263,715 |
| 4 | Steering ball joint dust covers | 10.3% | 0.81% | 12.4–12.9× | 82,994 |
| 5 | Brake pipes | 8.6% | 0.37% | 23.3–23.8× | 506,323 |
| 6 | Position lamp | 7.6% | 3.08% | 2.4–2.5× | 62,138 |
| 7 | Steering ball joints | 7.5% | 0.72% | 10.3–10.7× | 184,074 |
| 8 | Shock absorbers | 7.5% | 1.04% | 7.1–7.2× | 680,328 |
| 9 | Number plate lamps | 7.4% | 1.47% | 5.0–5.1× | 550,156 |
| 10 | Brake pads | 7.2% | 1.91% | 3.8× (3.76–3.81×) | 1,370,881 |
| 11 | Exhaust system | 7.2% | 1.01% | 7.0–7.2× | 406,960 |
| 12 | Indicators | 7.1% | 0.60% | 11.7–12.1× | 160,687 |
| 13 | Tyres | 7.1% | 3.75% | 1.9× (1.88–1.90×) | 1,777,826 |
| 14 | Headlamp | 6.6% | 2.39% | 2.7–2.8× | 79,770 |
| 15 | Brake performance (roller brake test) | 6.5% | 1.18% | 5.4–5.6× | 363,329 |
| 16 | Stop lamp | 6.4% | 2.51% | 2.5–2.6× | 94,485 |
| 17 | Wheel bearings | 5.8% | 0.42% | 13.7–14.4× | 106,759 |
| 18 | Tyre tread depth | 5.2% | 2.34% | 2.2× (2.20–2.22×) | 3,279,841 |
| 19 | Coil spring | 5.0% | 3.52% | 1.4× (1.40–1.43×) | 497,833 |
| 20 | Anti-roll bars | 5.0% | 0.75% | 6.5–6.8× | 131,733 |
| 21 | Wipers | 4.8% | 1.83% | 2.6–2.7× | 169,874 |
| 22 | Number plates | 3.6% | 0.26% | 13.6–14.2× | 332,842 |
| 23 | Brake discs | 3.3% | 0.71% | 4.6–4.7× | 2,034,606 |
| 24 | Seat belts | 2.5% | 0.33% | 7.2–7.9× | 89,570 |
| 25 | Sub-frame | 2.0% | 0.10% | 19.6–20.9× | 220,849 |
| 26 | Brake hoses | 1.7% | 0.12% | 13.2–14.5× | 104,135 |
| 27 | Road wheels | 1.2% | 0.41% | 2.8–3.1× | 144,791 |
| 28 | Engine oil leaks | 0.9% | 0.08% | 10.4–11.1× | 545,240 |
| 29 | Windscreen | 0.8% | 0.06% | 12.6–13.7× | 399,330 |
The pattern holds at every age
For the eight advisories testers give most often, the share that failed on the same part at the next MOT, by age at the first MOT. The small figure is the share for vehicles of the same ages without the advisory. Older vehicles fail more often either way, so each age is compared only with itself.
| Advisory on | 3 to 5 | 6 to 8 | 9 to 11 | 12 to 15 | 16 to 25 |
|---|---|---|---|---|---|
| Tyre tread depth | 3.6% 1.48% | 4.5% 1.95% | 5.2% 2.34% | 5.9% 2.62% | 6.2% 2.13% |
| Brake discs | 2.2% 0.33% | 2.8% 0.53% | 3.3% 0.71% | 3.7% 0.79% | 3.5% 0.68% |
| Tyres | 5.8% 3.22% | 6.3% 3.31% | 7.1% 3.75% | 8.1% 4.16% | 8.1% 3.55% |
| Brake pads | 6.2% 1.53% | 6.9% 1.78% | 7.2% 1.91% | 7.5% 1.91% | 7.5% 1.57% |
| Suspension arms | 6.7% 0.51% | 10.0% 1.92% | 11.9% 3.62% | 12.2% 4.73% | 12.0% 4.49% |
| Shock absorbers | 4.4% 0.25% | 6.6% 0.60% | 7.5% 1.04% | 8.8% 1.65% | 7.8% 1.54% |
| Number plate lamps | 7.4% 0.33% | 7.2% 0.73% | 7.4% 1.47% | 7.1% 2.07% | 6.2% 1.97% |
| Engine oil leaks | 0.5% 0.02% | 0.8% 0.04% | 0.9% 0.08% | 1.2% 0.17% | 1.3% 0.24% |
Many advisories are simply given again
At the next MOT the tester may advise on the part again, it may fail, or nothing may be recorded on it (often because it was repaired in between). Some vehicles are both advised on the part again and failed on it at the same test, so the three shares below add up to a little more than 100%. The parts testers most often advise on again:
- Brake pipes: 46.7% advised again, 8.6% failed, 48.4% nothing recorded (506,323 MOT tests with the advisory, vehicles aged 9 to 11).
- Sub-frame: 42.6% advised again, 2.0% failed, 55.7% nothing recorded (220,849 MOT tests with the advisory, vehicles aged 9 to 11).
- Number plates: 40.1% advised again, 3.6% failed, 56.8% nothing recorded (332,842 MOT tests with the advisory, vehicles aged 9 to 11).
- Engine oil leaks: 39.5% advised again, 0.9% failed, 59.7% nothing recorded (545,240 MOT tests with the advisory, vehicles aged 9 to 11).
- Windscreen: 39.2% advised again, 0.8% failed, 60.0% nothing recorded (399,330 MOT tests with the advisory, vehicles aged 9 to 11).
- Coil spring: 38.6% advised again, 5.0% failed, 58.2% nothing recorded (497,833 MOT tests with the advisory, vehicles aged 9 to 11).
How we worked it out
We took DVSA's anonymised MOT data for 2022 to 2025 [1] and paired each vehicle's normal MOT tests with its next one 300 to 500 days later: 83,372,892 pairs of class 4 tests (cars and light vans). For each part (a DVSA component) and each age band we counted the pairs whose first test recorded an advisory or a minor defect on it, and how many of those failed on the same part at the second test. A fail is DVSA's initial fail, including a fail fixed at the test station before the vehicle left (PRS).
The comparison group is every pair of the same age band whose first test recorded nothing on that part. Shares carry a 95% Wilson interval; ratios a 95% interval on the log scale. A part is ranked only if, at 9 to 11 years, at least 50,000 MOT tests recorded the advisory, at least 100 of those failed on it, at least 100 fails were expected at the no-advisory rate, the ratio's interval starts at 1.2 or higher, and the same holds in at least three of the five age bands.
Left out: DVSA's general and legacy advisories, warning lamps, headlamp aim, and two parts whose names overlap a larger one (the CSV keeps them, marked as not ranked). Common advisories that did not meet the rule: Transmission oil leaks, Swivel pins and bushes, Mirrors, MacPherson struts, Steering pins and bushes.
Limitation: Some owners repair an advised part before the next MOT, and those vehicles are still counted, so for a vehicle left as it was the chance of a fail is likely higher than these shares. A vehicle with an advisory differs from one without in more than that part (mileage, upkeep), so the ratio describes what happened, not what the advisory causes. MOTs record defects on the test day only. The same vehicle can appear in up to three pairs across these years, and the intervals treat each pair as independent, so they are approximate (somewhat too narrow). Vehicles not brought back for a test within 300 to 500 days are not in the pairs.
Download and reuse
Free to reuse under the Open Government Licence v3.0 with the credit "Source: VetTheCar analysis of DVSA MOT data (OGL v3)" and a link to this page. The CSV starts with the attribution rows and has every part at every age, ranked or not.
More from the MOT data
Questions people ask
Will a car with an MOT advisory fail its next MOT?
17.7% of MOT tests on vehicles aged 9 to 11 with a track rod end advisory were followed by a fail on it at the next MOT, the highest share of the 29 parts ranked here. Across those parts the share runs from 0.8% to 17.7%, each above the rate without the advisory.
Should I fix an advisory before the next MOT?
7.2% of brake pad advisories at 9 to 11 years were followed by a brake pad fail, against 1.9% without one. Ask a garage what the advisory means for that car: these shares are averages across 1,370,881 MOT tests, not a diagnosis.
Is an advisory a fail?
In all 83,372,892 pairs of MOT tests here, an advisory or a minor defect is a pass: the tester is noting a part that may need work. Only a major or dangerous defect fails the test.
Buying Report £14.99 incl. VAT · one car · no subscription · Not a mechanical inspection.
Sources
- Driver and Vehicle Standards Agency, Anonymised MOT tests and results, 2022 to 2025. DVSA MOT data, Open Government Licence v3.0. Accessed 7 Oct 2026.