Guide · based on 145 million tracked advisories
What MOT advisories mean
Advisory, minor, major, dangerous — what each grading actually commits you to, and which advisories are worth acting on first.
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An advisory is not a defect. It records something that still meets the standard but is heading the wrong way, and the certificate says monitor and repair if necessary. Most never become anything — conversion to a later failure runs from 18.7% for suspension down to 1.3% for oil leaks, so which advisory you have matters far more than having one.
18.7%
of suspension advisories return as a failure — the highest rate of any category
1.3%
of oil leak advisories do the same — the lowest, and a fourteenfold difference
376
days, median, from an advisory to the failure it becomes — when it becomes one
The four gradings, and what each one obliges you to do
Every item on the test lands in one of four buckets. Two let you drive away without doing anything, one lets you drive away but not pass, and one stops the car where it stands.
| Grading | Does it fail? | Can you drive? | What the certificate says |
|---|---|---|---|
| Advisory | No | Yes | Monitor and repair if necessary |
| Minor | No | Yes | Repair as soon as possible |
| Major | Yes | Not until repaired | Repair immediately |
| Dangerous | Yes | No — not anywhere | Do not drive until repaired |
A car passes with any number of advisories and any number of minor defects. It fails on a single major or dangerous one. Driving a vehicle in a dangerous condition risks a fine of up to £2,500 and points, and a dangerous grading applies even if your previous certificate still has months left on it.
The distinction people miss
An advisory and a minor defect look identical on the day — both pass, both let you drive off — but they are not the same statement. An advisory means the item still meets the standard. A minor means it has already fallen below the standard, just not far enough to matter for safety.
So a minor is the more serious of the two, despite feeling like the milder word. A split steering rack gaiter is a minor; the rack behind it is one of the more expensive things under a car, and the gaiter is all that keeps grit out of it.
Which advisories actually become failures
We followed 145 million individual advisories through the national record to see what happened to each one at the following test. The spread between categories is far wider than the word suggests.
The full picture, including what owners actually did
Conversion is only one of three outcomes. An advisory can also sit there untouched, or be dealt with — and the proportions say as much about the fault as the failure rate does.
| Category | Became a failure | Still there a year later | Dealt with |
|---|---|---|---|
| Suspension | 18.7% | 37.1% | 44.2% |
| Lamps and electrical | 14.4% | 24.9% | 60.7% |
| Body and exhaust | 11.8% | 28.2% | 60.0% |
| Tyres | 9.9% | 30.5% | 59.6% |
| Brakes | 9.4% | 36.1% | 54.4% |
| Structural corrosion | 6.7% | 17.5% | 75.9% |
| Axles and bearings | 6.5% | 23.8% | 69.7% |
| Oil leaks | 1.3% | 43.5% | 55.1% |
Outcomes measured at the following test on the same vehicle. Contains public sector information licensed under the Open Government Licence v3.0.
Two rows worth reading twice
Suspension holds both extremes at once. It is the likeliest to come back and the least likely to be dealt with, which is a combination no other category manages. The reason is silence: a wheel bearing hums and gets fixed 69.7% of the time, while a corroded spring makes no sound at all and gets fixed 44.2% of the time. Owners act on symptoms, not on paperwork.
Oil leaks look like neglect and are not. They are the most ignored advisory in the record at 43.5%, and also the one that almost never returns as a failure. Those two facts belong together — the wording is usually “oil leak, but not excessively”, and the gap between that and the failure threshold is enormous. Ignoring it is, on this evidence, a reasonable call.
The 376-day rule
When an advisory does convert, the timing is startlingly consistent — and it is the most useful thing on this page.
Eight defect categories, eight days apart. Suspension takes 376 days as a median, structural corrosion 384, and everything else lands between. That is one MOT cycle almost exactly, for materials with nothing in common: steel corroding over winters, rubber wearing by the mile, fluid degrading on a calendar.
If the figure were measuring deterioration, the medians would scatter across months. The most plausible reading is that it records when somebody decided to act — and that day is the next test, because it is the only date in a car’s year with a legal consequence attached.
The practical use is simple. Whatever is advised this year is, on the national evidence, a fair preview of next year’s bill. Price it the day you get the certificate and you have a twelve-month budget instead of a surprise.
What to do with yours
Decode the exact wording
The same six words can mean a ten-pound fix or a four-hundred-pound one. “Brake disc worn” and “brake disc worn, pitted or scored” are different findings with different urgency.
Our advisory checker translates 16 common phrasesGive it a deadline that is not the test
Everything converges on test day because nothing else has a date. Attach the repair to a service or a tyre change you were making anyway and the car gets a second deadline it will actually meet.
Batching works. The test need not be the batch.Separate what cannot wait
A tyre near the limit is an offence at the roadside today, whatever the certificate says. Structural corrosion fails without warning. Neither is a next-year problem.
£180–£460 pads and discs · £60–£120 per tyreRepeat advisories are the strongest signal on the certificate
One advisory is information. The same advisory three years running is a decision somebody kept making. It tells you the item has had three more years of whatever is wearing it, and that at least one owner looked at the cost and chose to leave it.
On a car you are buying, that is a price, not a worry. Every repeated line has a number attached, and those numbers are legitimately subtractable from an offer. Our used car check reads the whole history and prices each item, and how to read your MOT history covers what else to look for in the record.
Common questions
Do I have to fix an MOT advisory?
No. Your car has passed and an advisory carries no legal obligation. Whether it is worth doing depends entirely on which one — suspension advisories return as failures 18.7% of the time and oil leaks 1.3%, so the same word covers wildly different odds.
Is a minor defect worse than an advisory?
Yes, despite sounding milder. An advisory means the item still meets the standard and is simply heading the wrong way. A minor means it has already fallen below the standard, just not far enough to affect safety. Both pass, but only one is already a fault.
How soon does an advisory turn into a failure?
376 days as a median for suspension, up to 384 for structural corrosion — roughly one MOT cycle. Eight categories fall within eight days of each other, which suggests the figure is measuring when owners act rather than when parts wear out.
Which MOT advisory should I fix first?
Anything on the tyres, because tread below the limit is enforceable at the roadside regardless of your certificate, and anything structural, because it fails without warning. After that, suspension is the category most likely to return, and it is also the one that gives no symptom before it does.
Do advisories show up on a car’s public MOT history?
Yes. Every advisory is published against the registration and stays there, which is why repeated entries are such a useful signal when buying. It also means anyone can see what your car has been advised on, going back years.
Can a garage refuse to give me the car back over an advisory?
No. An advisory is a pass, and the car is yours to drive away. The only grading that stops you is dangerous, where the vehicle must not be driven at all until repaired — and that is a legal position rather than the garage’s preference.
We paired 216 million consecutive tests on the same vehicles and followed 145 million individual advisories forward to see what happened to that specific item — whether it failed, sat unresolved, or was dealt with. Figures are grouped by DVSA defect category rather than by individual component, so a category rate is an upper bound for any single part within it.
Thresholds and gradings are taken from the DVSA MOT inspection manual. Our full reference, what the MOT actually checks, goes through all eighteen sections of the test with the published figure behind each verdict.