At a glance
How 1,373 first tests went in 2025.
- Passed first time
- 67 in every 100
- Did not pass first time
- 33 in every 100448 failed first-attempt tests
- The typical car
- 18 yearsabout 121,411 miles
- First tests counted
- 1,373
What failed most often
- Suspension arm ball joint (front)15 in every 100 failed tests
- Tyre condition (front)14 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 2007 Mercedes-Benz CLS 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.
Tyres
Two wear patterns. The strongest is the tyre tread depth (rear): 3.0 times as often as on similar cars.
Figures below are measured across the 448 failed first attempts in 2025 that had a mileage recorded, which allows a like-for-like comparison.
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.
Tyre tread depth (rear)
What it means
Only primary grooves count when tread depth is assessed: those holding the wear indicators, or cut as deep as those when new. Shallower secondary grooves are ignored. Tread depth below the minimum for the vehicle is Dangerous, and so is a pattern not visible over the whole tread, but that second row applies only to vehicles that need the lower minimum.
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.
Brakes
Two faults. The strongest is the rigid brake pipes (rear): 2.5 times as often as on similar cars.
Rigid brake pipes (rear)
What it means
Chafing, corrosion or damage to a rigid brake pipe justifies rejection once its wall thickness is reduced by a set amount, although DVSA accepts this is not easy to determine. If a tester is not sure, the benefit of the doubt applies. A leaking pipe or connection is graded Dangerous on a hydraulic system and Major on an air system.
Anti-lock braking system (ABS)
What it means
ABS is failed as removed only where it has obviously been removed, because not every vehicle in the age range where removal is not permitted has ABS. A warning lamp that does not light or shows an ABS fault is Major, as is a missing or excessively damaged wheel speed sensor. Every failure row for this component is Major.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
Suspension
One fault: suspension arm ball joint (front), 2.4 times as often as on similar cars.
Suspension arm ball joint (front)
What it means
A suspension arm ball joint is failed under the general suspension pin, bush or joint wording. Excessively worn is Major, and likely to become detached is graded Dangerous.
Also noted as an advisory
Testers also noted it as an advisory, worn but not yet failing, on 48 first tests, 4.2 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.
Advisories
Other things testers noted as worn or close to failing, more often than on similar cars.
An advisory is a note from the tester about something that has not failed yet. It is an early warning, not a fail. Advisories for the faults above are shown with those faults.
Wheel bearings (front)
Rigid brake pipes (front)
Exhaust system (rear)
Flexible brake hoses (rear)
Suspension arm (rear)
Data: UK MOT open data, 2025. Counts cover advisories recorded on failed first tests only, 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
- 67in every 100
- Passed on the first test.
- Fixed at the station
- 6in every 100
- Failed, then fixed at the test station the same day.
- Failed
- 27in every 100
- Did not pass, and were not fixed at the test station.
First-attempt pass 67.4% of 1,373 first tests (2025): only cars that passed first time count. Official-style pass 73.3%: cars fixed at the test station also count as a pass. The 6 fixed and the 27 not fixed make the 33 in every 100 that did not pass first time.
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, 65 in every 100 passed first time.
| Year | Passed first time | First tests |
|---|---|---|
| 2005 | 71 in every 100 | 799 |
| 2006 | 70 in every 100 | 1,098 |
| 2007 This car | 67 in every 100 | 1,373 |
| 2008 | 69 in every 100 | 1,128 |
| 2009 | 66 in every 100 | 895 |
| 2010 | 65 in every 100 | 927 |
| 2011 | 73 in every 100 | 1,026 |
| 2012 | 74 in every 100 | 1,012 |
| 2013 | 71 in every 100 | 2,809 |
| 2014 | 74 in every 100 | 1,644 |
| 2015 | 78 in every 100 | 2,729 |
| 2016 | 79 in every 100 | 2,000 |
| 2017 | 80 in every 100 | 1,415 |
| 2018 | 83 in every 100 | 900 |
| 2019 | 82 in every 100 | 1,002 |
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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