At a glance
How 4,318 first tests went in 2025.
- Passed first time
- 74 in every 100
- Did not pass first time
- 26 in every 1001,116 failed first-attempt tests
- The typical car
- 12 yearsabout 62,646 miles
- First tests counted
- 4,318
What failed most often
- Tyre condition (front)19 in every 100 failed tests
- Coil spring (rear)12 in every 100 failed tests
- Anti-roll bar linkage ball joint dust cover (front)11 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 2013 Mercedes-Benz SLK 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.
Brakes
Three faults and one wear pattern. The strongest is the anti-lock braking system (ABS): 5.1 times as often as on similar cars.
Figures below are measured across the 1,114 of 1,116 failed first attempts (99.8%) 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.
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.
Electronic stability control
What it means
An ESC warning lamp is failed only when the tester is certain it indicates an ESC malfunction, because the lamp takes various forms and the owner's handbook may need checking. The system is also called ESP, VDC or DSC, among many other names. Every failure row is Major, covering the lamp, wheel speed sensors, wiring, other components and the switch.
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.
Brake discs (rear)
What it means
A brake disc or drum must be significantly worn before it is rejected, and being worn below the manufacturer's recommended limits is not a reason in itself. Significantly and obviously worn is Major, as is contamination with oil or grease. A disc or drum that is fractured, insecure, seriously weakened or missing is graded Dangerous.
Also noted as an advisory
Testers also noted it as an advisory, worn but not yet failing, on 144 first tests, 2.1 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
Four faults. The strongest is the anti-roll bar ball joint dust cover (front): 4.5 times as often as on similar cars.
Anti-roll bar ball joint dust cover (front)
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.
Coil spring (rear)
What it means
A missing bump stop rubber is not a reason to fail a coil spring. When the vehicle is jacked and lowered, a spring that does not correctly locate as the suspension returns to its normal running position is rejected as insecurely attached. A missing spring is Major, and graded Dangerous where directional control is affected.
Shock absorbers (front)
What it means
Slight seepage that leaves a film of fluid on a shock absorber does not fail it. Severe leakage, or damage so that it does not function, is Major. A shock absorber missing or likely to become detached is graded Dangerous, though a missing one is only rejected if shock absorbers were fitted as standard.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
Tyres
Two wear patterns. The strongest is the tyre tread depth (rear): 4.2 times as often as on similar cars.
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.
Also noted as an advisory
Testers also noted it as an advisory, worn but not yet failing, on 190 first tests, 2.0 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. 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)
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
- 74in 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
- 23in every 100
- Did not pass, and were not fixed at the test station.
First-attempt pass 74.2% of 4,318 first tests (2025): only cars that passed first time count. Official-style pass 76.5%: cars fixed at the test station also count as a pass. The 3 fixed and the 23 not fixed make the 26 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, 75 in every 100 passed first time.
| Year | Passed first time | First tests |
|---|---|---|
| 1997 | 68 in every 100 | 551 |
| 1998 | 70 in every 100 | 846 |
| 1999 | 71 in every 100 | 1,157 |
| 2000 | 69 in every 100 | 1,457 |
| 2001 | 70 in every 100 | 1,784 |
| 2002 | 71 in every 100 | 1,588 |
| 2003 | 67 in every 100 | 1,449 |
| 2004 | 66 in every 100 | 2,631 |
| 2005 | 67 in every 100 | 4,173 |
| 2006 | 67 in every 100 | 3,277 |
| 2007 | 67 in every 100 | 3,223 |
| 2008 | 67 in every 100 | 2,946 |
| 2009 | 69 in every 100 | 2,332 |
| 2010 | 70 in every 100 | 1,935 |
| 2011 | 75 in every 100 | 2,396 |
| 2012 | 74 in every 100 | 5,259 |
| 2013 This car | 74 in every 100 | 4,318 |
| 2014 | 76 in every 100 | 4,621 |
| 2015 | 80 in every 100 | 4,657 |
| 2016 | 82 in every 100 | 1,193 |
If you are buying one
What this year's MOT record means for the decision in front of you.
Mileage matters most on a 2013 Mercedes-Benz SLK.
Of 2013 Mercedes-Benz SLK vehicles with under 44,000 miles, 87 in every 100 passed their 2025 MOT first time. With 87,000 miles or more, 64 in every 100 did.
Petrol or diesel?
| Typical mileage | Passed first time, as tested | Passed first time, same mileage | |
|---|---|---|---|
| Diesel | 66,952 miles | 72 | 73 |
| Petrol | 51,383 miles | 80 | 76 |
Figures are in every 100 first tests. Petrol cars look better on the raw figures only because diesel cars have done more miles (typically 66,952 against 51,383). 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 44,000 | 57,000–69,000 | 87,000 and over | |
|---|---|---|---|
| Tyre condition (front) | 2.3 | 4.5 | 7.1 |
| Coil spring (rear) | 2.2 | 2.5 | 3.2 |
| Anti-roll bar linkage ball joint dust cover (front) | 0.6 | 3.0 | 5.1 |
| Tyre tread depth (rear) | 0.8 | 2.4 | 4.1 |
| Suspension arm ball joint (front) | 0.3 | 1.9 | 4.7 |
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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