Data study
What actually predicts an MOT pass
Data updated
By Andrew Pickett, Editor at The MOT Files. Published by Omega IT.
Quick answer
Across 33,210,950 MOT tests, wear matters most: 87.2% of three-to-five-year-old cars pass against 58.9% at fifteen-plus, and mileage tracks it almost exactly, each moving the rate by about 29 points. After adjusting for both, engine size still moves it 14 points and region 11. Colour moves it 3.9 points and the month of the test 1.2 — both close to nothing.
Ask what makes a car pass its MOT and you get folklore: book in summer, avoid white cars, small engines are simpler. The DVSA dataset records the colour, engine size, test date and test location of every car, so each of those can be checked. Four of the six factors below are shown after adjusting for the age and mileage of the cars, because without that every one of them is secretly a measurement of age.
The six factors, ordered
How much each one moves the pass rate
- 1.Mileagethe thing itself28.9 pts
- 2.Agethe thing itself28.4 pts
- 3.Engine sizeadjusted for age and mileage13.9 pts
- 4.Where it livesadjusted for age and mileage10.5 pts
- 5.Colouradjusted for age and mileage3.9 pts
- 6.Month of testadjusted for age and mileage1.2 pts
Spread between the best and worst level of each factor. Age and mileage are shown raw because they are what everything else is adjusted for.
Factor one
Age
Age and mileage are the two big levers, and they are very nearly the same lever: a 28-point spread for age, 29 for mileage, both measuring how much a car has worn. The pass rate falls in every age band, and a fifteen-year-old car passes at roughly 67% of the rate a three-year-old one does. This is why every comparison on this site is adjusted for both, and why a ranking that is not is a ranking of how recently the cars were bought.
Factor two
Mileage
The second lever, and entangled with the first: high mileage mostly means old. Even so, within an age band a car that has covered more ground has worn more, which is why the two are crossed into twenty-five cells before any model or area is compared.
Factor three · adjusted
Engine size
A 14-point gradient that survives the adjustment. Small engines look strong raw — they sit in new cars — and weak once age is removed. The likeliest reading is not mechanical. A three-litre car is an expensive car, serviced on schedule and put through the test with new tyres; a one-litre car is a budget car, and a budget car is run on a budget. The adjustment removes age and mileage. It cannot remove money, and this is what money looks like.
Factor four · adjusted
Where the car lives
11 points between London and Scotland, after adjustment. The failure items explain it: corrosion is recorded many times more often on failed Scottish and coastal cars than on London ones. Every postcode area is ranked here, with its own failure profile.
Factor five · adjusted
Colour
3.9 points across every colour with at least 100,000 tests. The raw figures tell a livelier story, and it is the wrong one: white cars pass 72.2% raw and 71.1% adjusted, silver 68.2% raw and 72.6% adjusted. White is fashionable now and silver was fashionable in 2008, so the raw gap is fleet age in disguise. Colour does not predict an MOT result.
Factor six · adjusted
Month of the test
1.2 points between the best month and the worst. The advice to avoid winter because lamps and tyres fail more in the dark and wet is intuitive and, on 33,210,950 tests, not true to any degree that matters. Book the test when it is due.
How this was worked out
Method and limits
Source: the DVSA anonymised MOT testing dataset under the Open Government Licence, 33,210,950 class 4 initial tests, retests and abandoned tests excluded. Age and mileage are shown as recorded. Engine size, region, colour and month are each split into twenty-five age and mileage cells and reweighted onto the national profile — direct standardisation, the same method as every model ranking on this site.
The adjustment isolates each factor from age and mileage. It does not isolate it from everything: engine size is confounded with price and upkeep, region with income and road type. The figures are what the data shows; the explanations are the most plausible readings of it, and are labelled as such.
For journalists and researchers
Use this data
Republish freely with attribution, under the same Open Government Licence as the underlying data. Credit The MOT Files with a link and name DVSA as the source.
Plain citation
The MOT Files (2026). What actually predicts an MOT pass: 33,210,950 tests, six factors. Derived from the DVSA anonymised MOT testing dataset under the Open Government Licence v3.0. https://motfiles.co.uk/what-predicts-an-mot-pass
HTML, with the attribution link
<p>Source: <a href="https://motfiles.co.uk/what-predicts-an-mot-pass">What predicts an MOT pass, The MOT Files</a> — analysis of 33,210,950 DVSA MOT tests, adjusted for vehicle age and mileage.</p>Common questions
- Does the colour of a car affect whether it passes its MOT?
- Barely. Once age and mileage are accounted for, the colours with at least 100,000 tests span 3.9 percentage points, from bronze at 74.3% to yellow at 70.4%. Raw figures suggest more, because colour fashions change: white cars are young and silver cars are old, so an unadjusted comparison is really an age comparison wearing a coat of paint.
- Is there a best month to book an MOT?
- Not meaningfully. Adjusted pass rates by month run from 71.5% in April to 72.7% in December, a range of 1.2 points. The belief that winter tests fail more on lights and tyres does not survive the data. Book when it is due.
- Do bigger engines pass the MOT more often?
- Yes, and by a lot: 82.2% for engines over three litres against 68.5% for engines under one litre, after adjusting for age and mileage. That is not the engine itself. Larger engines sit in more expensive cars maintained to a higher standard, and the adjustment removes age and mileage but not money. It is the clearest sign in the data that upkeep, not engineering, drives most MOT outcomes.
- What is the single biggest predictor of an MOT pass?
- Wear, measured either way. 87.2% of cars aged three to five pass against 58.9% at fifteen or more, a 28-point gap; cars under 30,000 miles pass 88.3% against 59.4% over 120,000, a 29-point gap. The two are close to interchangeable and dwarf everything else, which is why every comparison on this site is adjusted for both.
- Why does where a car lives matter?
- 77.1% in London against 66.6% in Scotland, after adjustment. The failure items point at corrosion: road salt and sea air. Full area-by-area figures are on the MOT by area pages.
Analysis built from DVSA data of