Our own MOT research
Your car passed its MOT. It was still warned about something.
A pass is not a clean bill of health. Our own analysis of 210,390 MOT tests in the Cambridge postcode area found that nearly half the cars that passed were still advised on something. An advisory is the tester telling you a part is on its way out but has not got bad enough to fail yet, and it is the single most useful thing on the certificate most people never read.
What an advisory actually is
Nearly half the cars that passed their MOT were still warned about something: 48.8% of passes carried an advisory.
An MOT has two outcomes that matter. A failure means the car cannot legally be used until it is fixed. An advisory means the tester has seen something worn, corroded or close to a limit, and is writing it down so you know.
Nothing happens as a result. There is no follow-up, no reminder and no requirement to act. It sits on the certificate and waits for you to look at it, which is why so many are never dealt with until the following year, when they have become the failure instead.
What an advisory predicts
We matched cars across two years of tests to see what happened next. The pattern is the same in every category: a car advised on something is far more likely to fail on that same thing at its next test than a car that was not.
Brakes are the clearest example and the one worth acting on soonest. Of the cars advised on their brakes, 9.25% failed on brakes the following year, against 3.91% of the cars that were not advised. That is more than double, and brakes are the system with the least margin in it.
| Advised on | Failed next year after an advisory | Failed next year without one |
|---|---|---|
| Steering | 17.02% of 1,798 | 1.59% of 122,332 |
| Lamps and electrics | 27.91% of 3,458 | 11.27% of 120,672 |
| Suspension | 17.21% of 19,527 | 7.06% of 104,603 |
| Brakes | 9.25% of 26,358 | 3.91% of 97,772 |
| Tyres | 11.7% of 35,595 | 6.44% of 88,535 |
Why a pass still leaves you guessing
The MOT is a minimum safety standard on one day, not an inspection of how the car is doing. It does not check the clutch, the gearbox, the cambelt, the condition of the oil or anything about how the engine is running. A car can pass in the morning and be genuinely due a lot of work in the afternoon, and both things are true at once.
That is the gap an advisory half fills, and it only half fills it, because the tester is looking at the items on the test and nothing else.
What to do with one
Read it, which sounds obvious and is the step most people skip. Then get the items priced rather than guessed at, because the gap between an advisory that can wait a year and one that should be done this month is large and is not obvious from the wording.
The cheapest time to deal with an advisory is while it is still an advisory. Once it is a failure the car is off the road until it is fixed, and you are paying on somebody else's timetable rather than your own.
That is the whole argument for getting it looked at while nothing is urgent: you keep the timetable. It is also why this sort of work suits somebody coming to the car rather than the car going anywhere, because at that point there is nothing wrong with it that stops you driving it.
What this does not show
This is one year in one postcode area, not a census and not a national picture. It is directional, and a row with fewer cars behind it carries less weight.
An advisory does not cause a failure. Both follow from the condition of the car. The advisory is the early sighting of the same wear, not the reason for it.
Not every car comes back. Of the cars tested in the earlier year, about a third did not appear again in the later one. They were sold, scrapped, untested that year or re-registered, and this data cannot tell those apart. The matched set is 124,130 cars.
CB is not Cambridgeshire. The postcode area takes in Newmarket and Haverhill in Suffolk and Saffron Walden in Essex, and leaves out Peterborough, Huntingdon, March and Wisbech.
If there is an advisory sitting on your certificate, the useful next step is finding out which items actually need doing and roughly what each one costs, which is part of a full service or a standalone check.
Got an advisory on your certificate?
Send us what it says and we will tell you which items need doing now, which can wait, and what each one costs. At your home or work across Soham, Ely, Newmarket, Cambridge and Huntingdon.
Flat £20 call-out, no mileage charges. 5.0 from 9 reviews on Google.
Related: our full MOT research, MOT advisories explained, what is checked in an MOT, our pre-MOT check.