Our own MOT research
Does mileage or age matter more for an MOT?
Mileage. In our own analysis of 166,908 MOT tests in the Cambridge postcode area, a car of 12 to 15 years with under 25,000 miles on it failed 10.2% of the time, while a far younger car of 5 to 8 years that had done over 125,000 failed 20.7% of the time. The older car was the safer bet, by about half.
What the numbers show
The table reads across, not down. Each column holds the age of the car still, so the only thing changing along a column is how far it has been driven. Find the row for your own mileage and the column for your own car.
The pattern holds in every column. Across the mileage range the failure rate roughly triples, and it does that whether the car is 5 to 8, 9 to 11 or 12 to 15 years old. Age still matters, which is why each column sits a little higher than the one before it. It just matters less than the odometer does.
| Miles on the clock | 5 to 8 years old | 9 to 11 years old | 12 to 15 years old |
|---|---|---|---|
| under 25k | 7.6% of 4,888 | 7.8% of 1,296 | 10.2% of 588 |
| 25k to 49k | 10.8% of 19,586 | 13.1% of 6,888 | 16% of 3,497 |
| 50k to 74k | 14.6% of 21,051 | 17.6% of 13,422 | 21.7% of 8,129 |
| 75k to 99k | 18.2% of 11,579 | 21.3% of 14,503 | 26.3% of 12,246 |
| 100k to 124k | 19.5% of 4,503 | 23.4% of 9,320 | 27.2% of 11,305 |
| 125k to 149k | 20.7% of 3,136 | 25.2% of 7,293 | 28.4% of 13,678 |
Why mileage does the damage
Almost everything an MOT tests wears out by being used rather than by getting older. Brake pads and discs wear by stopping the car. Tyres wear by turning. Suspension joints and bushes wear by moving. A car sitting on a drive is doing none of that.
Time does its own damage, and that is real: rubber perishes, metal corrodes, fluid absorbs water whether you drive or not. But the parts that fail an MOT most often are the ones that have been working, and work is measured in miles.
What it means for when you service your car
Most people go by the date. The car was serviced last autumn, so it is due again this autumn. That works fine for an average car doing average miles, and it is the wrong guide for anything else.
If you are high up the table for your age, the calendar is flattering you. A car three years old on 90,000 motorway miles is wearing like something much older, and the service book will not say so. The other way round holds too: a low-mileage car is often being serviced more often than it needs, and the honest answer there is that it can wait.
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 tests behind it carries less weight.
Mileage is recorded, not verified. The figure is what the tester entered on the day, and the data carries no way to check it.
High mileage does not cause a failure. Both follow from how much the car has been used and how it has been looked after. A high-mileage car that has been maintained properly can and does pass.
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. Nothing here may be read as a county figure or attributed to a town.
If you have just worked out that your car is higher up that table than you thought, the useful next step is finding out what it would actually fail on, which is what a full service is for.
Find out where your car actually stands
Tell us the car and roughly what it has done, and we will tell you what it needs and what it costs, before anything starts. We come to 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, service intervals explained, how often to service your car, our pre-MOT check.