MOT advisory “On or after 01/07/2008 emits excessive smoke or vapour but not likely to obscure the vision of other road users” — meaning and what to do
Last updated · OBDCode UK editorial
In plain English: the tester noted a noise, emissions or leaks item that was not a fail on that MOT. Fix soon.
Can you drive with this?
Limit driving. Limit driving to short essential trips until a garage has assessed it. Avoid hard loads, towing, and long motorway runs.
Carbon monoxide. Never idle in a closed garage to read codes — an open door is not enough. CO is odourless and can kill. Run diagnostics in open air. Headache or nausea with exhaust smell: get fresh air and stop.
What the tester saw
MOT testers work from the DVSA inspection manual. For this item the manual wording is “Exhaust emits excessive smoke or vapour of any colour to an extent likely to obscure the vision of other road users.”. In plain English: the tester judged that wear or deterioration on the on or after 01/07/2008 had not gone far enough to reject at that test. That is why it was recorded as an advisory rather than a failure. It is not a statement about the vehicle’s condition or legal status today.
If it worsens to the manual fail wording above, DVSA would class that defect as Dangerous. That grade describes the fail threshold, not the recorded advisory.
Do you need to fix it?
An advisory did not affect that test’s result. It is the tester telling you what is likely to need attention, and how soon depends on the item.
- Fix soon. Excessive smoke or vapour that does not yet obscure vision should be diagnosed within a few weeks. Escalate if vision is affected, smoke thickens, or you smell exhaust in the cabin.
- Can you DIY? We do not publish DIY repair or strip-down steps for this advisory. External look-over only; leave structural, brake hydraulic, fuel, steering, or restraint work to a qualified garage.
- Buying a used car? Repeated advisories for the same item across several years of MOT history mean the owner has been ignoring it. Check the car’s full record with our free MOT history check.
What happened to other cars with this advisory
These figures are a statistical association from the national MOT extracts. They are not a prediction about this car, and we have not inspected it.
Their rate of failing a 2025 MOT for any reason was 27.3% (95% CI 25.6–29.0), against 18.2% (95% CI 18.2–18.2) for cars that passed without this advisory.
The same 2,715 cars were 17.5 percentage points more likely not to be tested again in 2025 (24.8% (95% CI 23.2–26.4) versus 7.3% (95% CI 7.3–7.3) for cars without the advisory). The extracts do not record scrappage; a missing later test is the public signal that the vehicle was not presented.
The median car in this cohort was 14.0 years old with 126,981 miles at the 2024 test.
By age at the 2024 test
Scroll horizontally to read every age column.
| Age | Cars | Same-item fail | Not tested again |
|---|---|---|---|
| 8–12 years | 381 | 0% (95% CI 0.0–1.0) | 17.6% (95% CI 14.1–21.7) |
| 12–16 years | 1,791 | 0.73% (95% CI 0.4–1.2) | 25.1% (95% CI 23.1–27.1) |
| 16 years and over | 528 | 0.38% (95% CI 0.1–1.4) | 29.5% (95% CI 25.8–33.6) |
By mileage at the 2024 test
Scroll horizontally to read every mileage column.
| Mileage | Cars | Same-item fail | Not tested again |
|---|---|---|---|
| 80,000–120,000 miles | 843 | 0.59% (95% CI 0.3–1.4) | 18.4% (95% CI 15.9–21.1) |
| 120,000 miles and over | 1,525 | 0.46% (95% CI 0.2–0.9) | 31.5% (95% CI 29.3–33.9) |
A robustness re-run on the 1,293 cars tested in January–June 2024 only — so the next annual test almost always falls inside 2025 — found a same-item fail rate of 0.62% (95% CI 0.3–1.2) and a not-retested gap of +16.1 points. A December 2024 test may not be due until 2026, which can make a car look as if it vanished; the first-half window removes most of that censoring.
Of the 1,833 cars that failed on this line in 2024, 2.0% (95% CI 1.5–2.8) failed on it again in 2025 — 438 times the rate for cars that did not fail on this item, and 31.0% (95% CI 29.0–33.2) of those 1,833 cars that failed were not tested again. Did this failure stay fixed?
Follow-up uses the DVSA vehicle_id, which is stable across annual releases, so the same physical car is compared from its 2024 test to its 2025 test. Browse the MOT prognosis registry. Source: DVSA Anonymised MOT tests and results, 2024 and 2025 extracts (Class 4). Contains public sector information licensed under the Open Government Licence v3.0.
Related noise, emissions and leaks advisories
Before you agree to the work
A fault or an advisory is a quote waiting to happen. These pages set out what a garage has to tell you, what a comparable written quote should include, and what you can do if the bill is not what you agreed.
- Estimates, quotes and extra work — what a price has to cover, and when a garage may charge more than it first said.
- What a diagnostic test costs — what the fee should include, and when it should come off the repair.
- Tools — when to buy and when to skip — how to choose a diagnostic tool, and when a garage visit is cheaper than owning one.
- Choosing a garage you can check — what to verify before you hand over the keys.
- Your rights after a car repair — what to do when the work is not right, and how to put it in writing.
Frequency: DVSA Anonymised MOT tests and results, 2025 extract (Class 4). Wording follows the DVSA inspection manual. Contains public sector information licensed under the Open Government Licence v3.0.