50,204 tests in 2025
Mercedes-Benz Slk reliability and MOT pass rate
75.4% passed first time. The 24.6% fail rate is 2.0 points worse than the all-car average, on a median example 16 years old with 68,875 miles.
MOT pass rates / Mercedes-Benz
Pass rate
75.4%
22.6% of all cars failed; 24.6% of these did.
Fixed on the day
3.6%
Passed after a defect was put right during the visit.
Median at test
68,875 mi
16 years old.
Fail rate by age
| Age at test | Tests | Fail rate |
|---|---|---|
| 3-5 years | 0 | — |
| 6-9 years | 1,146 | 16.3% |
| 10-13 years | 18,087 | 21.7% |
| 14+ years | 30,971 | 26.6% |
What the Slk fails on
Share of failed tests with at least one fail item in each DVSA inspection section. A test can fail in several sections at once.
- Suspension254 dangerous50.1%
- Tyres3,454 dangerous24.8%
- Brakes918 dangerous24.6%
- Lamps, reflectors and electrical equipment50 dangerous23.2%
- Visibility5 dangerous10.6%
- Noise, emissions and leaks10 dangerous9.5%
- Body, chassis, structure57 dangerous5.4%
- Seat belts and supplementary restraint systems1 dangerous5.2%
Is the Slk getting worse?
The fail rate rose 2.2 points to 24.6% from 2022 to 2025 while the median one tested aged 2 years, which is about what ageing alone predicts (2.4 points). Read it as the fleet getting older rather than the model changing.
| Year | Tests | Median age | Fail rate | All cars | |
|---|---|---|---|---|---|
| 2022 | 61,156 | 14 | 22.4% | 22.5% | |
| 2023 | 59,311 | 15 | 23.6% | 22.8% | |
| 2024 | 48,865 | 16 | 24.7% | 23.2% | |
| 2025 | 50,148 | 16 | 24.6% | 22.6% |
Fail rate is first attempts at class 4 tests. Median age is the age of a typical Slk at its test that year, and it is the number to watch: across the whole fleet each extra year of age adds roughly 1.9 points to the fail rate, so a model whose age and fail rate rise together is simply getting older.
The exact defects that fail it
Every failure item DVSA recorded against a Slk in 2025, counted by how many tests each one appeared on.
- 1Coil spring: fractured or broken2,509 tests
- 2Ball joint: ball joint excessively worn1,519 tests
- 3Tread depth: tread depth below requirements of 1.6mm992 tests
- 4Condition: has ply or cords exposed845 tests
- 5Rigid brake pipes: excessively corroded724 tests
- 6Malfunction indicator lamp: inoperative or indicates a malfunction685 tests
- 7Condition: has a cut in excess of the requirements deep enough to reach the ply or cords648 tests
- 8Pins and bushes: pin or bush excessively worn646 tests
What wears out first
Advisories are the tester flagging wear that is still legal. A typical Slk collects 2.92 of them per test, and these are the ones that come up most. Treat it as the running-repairs list for the next year or two.
- 1Tread depth: tread depth below requirements of 1.6mm7,154 tests
- 2Rigid brake pipes: excessively corroded5,764 tests
- 3Condition: has a tear, caused by separation or partial failure of its structure4,297 tests
- 4Brake discs: in such a condition that it is seriously weakened4,256 tests
- 5Pins and bushes: pin or bush excessively worn2,779 tests
- 6Brake pads: less than 1.5 mm thick2,591 tests
- 7Wheel bearings: has excessive play2,404 tests
- 8Engine oil leaks: leaking excessively from engine2,110 tests
Questions
What is the Mercedes-Benz Slk MOT pass rate?
75.4% of the 50,204 Mercedes-Benz Slk first-attempt MOTs in 2025 passed. The fail rate of 24.6% compares with 22.6% across all cars. A further 3.6% passed after a defect was fixed during the test visit.
What does a Mercedes-Benz Slk usually fail on?
The single most common failure is "Coil spring: fractured or broken", recorded on 2,509 failed tests, followed by "Ball joint: ball joint excessively worn" and "Tread depth: tread depth below requirements of 1.6mm". By section, suspension appears in 50.1% of failures, tyres appears in 24.8% of failures, brakes appears in 24.6% of failures.
Does age change the odds?
Sharply. At 3 to 5 years old the fail rate was n/a%; at 14+ years it was 26.6%. The median Mercedes-Benz Slk tested in 2025 was 16 years old with 68,875 miles.
Is the Mercedes-Benz Slk getting less reliable?
The fail rate rose 2.2 points to 24.6% from 2022 to 2025 while the median one tested aged 2 years, which is about what ageing alone predicts (2.4 points). Read it as the fleet getting older rather than the model changing.
First-attempt class 4 tests, 2025, from DVSA’s anonymised MOT data (OGL v3, retrieved 2026-09-12). DVSA records newer cars trim by trim; this page adds every Slk trim together. Year-on-year figures come from the same DVSA extracts for 2026 and earlier years. Full method on the pass rates hub.
DVSA has published 18 safety recalls naming the Mercedes-Benz Slk: Mercedes-Benz Slk recalls.
Other Mercedes-Benz models
Checking a particular Slk?
The odds above are the model. The car in front of you has its own record: every test, every advisory, the mileage at each one.
Due a test? Find an approved MOT station near you.