At a glance
How 7,956 first tests went in 2025.
- Passed first time
- 80 in every 100
- Did not pass first time
- 20 in every 1001,615 failed first-attempt tests
- The typical car
- 7 yearsabout 57,004 miles
- First tests counted
- 7,956
What failed most often
- Tyre condition (front)21 in every 100 failed tests
- Tyre tread depth (front)9 in every 100 failed tests
- Windscreen washers7 in every 100 failed tests
How we count this. Data: UK MOT open data, 2025. Only Class 4 cars on their first MOT of the year are counted. A car that fails and is fixed at the test station still counts as a fail in the first-attempt rate. These are raw results, not adjusted for age, mileage, or peer mix. The MOT does not test engine or gearbox internals.
These are patterns across 2018 Mercedes-Benz CLA vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. A wear pattern follows age and use more than the way the car was built. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.
Road wheels
One fault: wheel condition (front), 13 times as often as on similar cars.
Figures below are measured across the 1,614 of 1,615 failed first attempts (99.9%) that recorded an odometer reading in 2025. Mileage is needed to compare like with like.
We only list faults with at least 20 failures and a rate of about 2.0 times that of similar cars, which keeps one-off results out of the list.
Wheel condition (front)
What it means
A wheel with any fracture or welding defect is graded Dangerous. So is a tyre retaining ring likely to come off, or a wheel distorted or worn to the extent that the wheel or tyre is likely to become detached. A wheel that is badly distorted, or has an excessively worn spigot mounting, is graded Major.
Also noted as an advisory
Testers also noted it as an advisory, worn but not yet failing, on 30 first tests, 2.2 times as often as on similar cars.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.
Lamps and electrical
One fault: individual direction indicators (rear), 4.6 times as often as on similar cars.
Individual direction indicators (rear)
What it means
Direction indicators must be amber, though vehicles first used before a set date may have white at the front and red at the rear when the indicators are combined with stop or position lamps, and sequential or dynamic ones are not a reason to fail. A lamp that is missing, inoperative or has more than half of a multiple light source not functioning is graded Major. A flashing rate outside the permitted range is graded Minor.
Also noted as an advisory
Testers also noted it as an advisory, worn but not yet failing, on 33 first tests, 5.5 times as often as on similar cars.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.
Suspension
One fault: anti-roll bar linkage ball joint dust cover (front), 3.4 times as often as on similar cars.
Anti-roll bar linkage ball joint dust cover (front)
What it means
A suspension joint dust cover that is severely deteriorated is Minor. It becomes Major once it is missing or no longer prevents the ingress of dirt, so what matters is whether it still keeps dirt out. DVSA words this for any suspension joint dust cover, and files it here under anti-roll bars.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
Tyres
One wear pattern: tyre condition (front), 2.1 times as often as on similar cars.
Tyre condition (front)
What it means
Exposed or damaged ply or cords are graded Dangerous. A cut in excess of the requirements and deep enough to reach the ply or cords is Major, and testers may open the cut with a blunt instrument to check its depth. A tyre contacting the vehicle through flexing or suspension movement is not a defect; fouling fails only at the time of test.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
Noise, emissions and leaks
One fault: petrol engine warning light, 2.1 times as often as on similar cars.
Petrol engine warning light
What it means
The malfunction indicator lamp (MIL) on a petrol engine is a Major failure when it is illuminated indicating a malfunction. The detail line DVSA gives for the same row also names an inoperative lamp. The test covers only certain petrol vehicles, depending on their age, size and fuel type.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
MOT pass rates
How first tests ended, and how the pass rates are counted.
- Passed first time
- 80in every 100
- Passed on the first test.
- Fixed at the station
- 3in every 100
- Failed, then fixed at the test station the same day.
- Failed
- 17in every 100
- Did not pass, and were not fixed at the test station.
First-attempt pass 79.7% of 7,956 first tests (2025): only cars that passed first time count. Official-style pass 82.8%: cars fixed at the test station also count as a pass. The 3 fixed and the 17 not fixed make the 20 in every 100 that did not pass first time.
Petrol and diesel
Figures are in every 100 first tests. Cars with more miles usually fail more often, so the same-mileage figure gives every fuel the mileage mix of all the cars in this year.
Same model, other years
Passed first time in every 100, all tested in 2025.
Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 81 in every 100 passed first time.
| Year | Passed first time | First tests |
|---|---|---|
| 2013 | 69 in every 100 | 1,981 |
| 2014 | 71 in every 100 | 4,076 |
| 2015 | 73 in every 100 | 6,449 |
| 2016 | 75 in every 100 | 7,223 |
| 2017 | 77 in every 100 | 7,815 |
| 2018 This car | 80 in every 100 | 7,956 |
| 2019 | 83 in every 100 | 7,812 |
| 2020 | 84 in every 100 | 7,032 |
| 2021 | 86 in every 100 | 9,055 |
| 2022 | 87 in every 100 | 10,638 |
If you are buying one
What this year's MOT record means for the decision in front of you.
Mileage matters most on a 2018 Mercedes-Benz CLA.
Of 2018 Mercedes-Benz CLA vehicles with under 41,000 miles, 86 in every 100 passed their 2025 MOT first time. With 77,000 miles or more, 73 in every 100 did.
Petrol or diesel?
| Typical mileage | Passed first time, as tested | Passed first time, same mileage | |
|---|---|---|---|
| Petrol | 52,460 miles | 81 | 80 |
| Diesel | 64,024 miles | 78 | 79 |
Figures are in every 100 first tests. Petrol cars look better on the raw figures only because diesel cars have done more miles (typically 64,024 against 52,460). At the same mileage there is no clear difference between the two.
What to check at your mileage
How often each fault turned up on a failed first test, by the car's mileage. Read it as: what is likely to need looking at on a car like the one in front of you.
| Under 41,000 | 52,000–62,000 | 77,000 and over | |
|---|---|---|---|
| Tyre condition (front) | 3.6 | 3.9 | 4.6 |
| Tyre tread depth (front) | 1.1 | 1.6 | 2.0 |
| Windscreen washers | 1.0 | 1.5 | 1.7 |
| Coil spring (rear) | 0.7 | 1.0 | 2.5 |
| Petrol engine warning light | 0.6 | 1.3 | 1.7 |
Faults per 100 first tests, by the car's mileage at the test.
When a car fails
of failed cars had one item to fix.
of failed cars had three or more items to fix.
of all first tests had a defect the tester marked dangerous (unsafe to drive away).
Every figure here is a first-attempt MOT rate from DVSA open data for this model line, for cars of this model year tested in 2025. Each mileage band holds a fifth of the tests. MOTs do not test engine or gearbox internals, so this is a pre-purchase checklist, not a full reliability score.
FAQs
Short answers about how to read this model-year guide.
About this data
How this page is built and what it can (and can't) say.
These figures come from UK MOT open data for this model year. We surface common failure patterns against similar cars, not a full reliability score, and not a pass/fail verdict on any individual vehicle.
What we include
UK Class 4 cars only. Normal MOT tests (not retests); first test per vehicle per calendar year; results pass, PRS, or fail.
Same-day repairs
PRS means the car failed items that were fixed at the test station and then passed the same day. We count PRS as a first-attempt fail in headline rates so same-day repairs do not hide problems.
How we compare
We compare this model year with other Class 4 cars of similar age and mileage in the same test year. This model family is left out of the peer group so the car is not measured against itself.
What this does not cover
- MOTs do not cover engine internals, gearboxes, or many electronics; this is not a full reliability score.
- Common faults come from MOT defect stats, not manufacturer TSBs or recalls.
- Age and mileage matching reduces, but does not remove, differences in how cars were used and maintained.
- If the data for a car is too thin to say anything useful, we say so rather than guess.
Contains public sector information licensed under the Open Government Licence v3.0.
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