19,227 tests in 2025
Mercedes-Benz Sl reliability and MOT pass rate
85.2% passed first time. The 14.8% fail rate is 7.8 points better than the all-car average, on a median example 21 years old with 64,676 miles.
MOT pass rates / Mercedes-Benz
Pass rate
85.2%
22.6% of all cars failed; 14.8% of these did.
Fixed on the day
2.4%
Passed after a defect was put right during the visit.
Median at test
64,676 mi
21 years old.
Fail rate by age
| Age at test | Tests | Fail rate |
|---|---|---|
| 3-5 years | 227 | 9.3% |
| 6-9 years | 2,008 | 8.2% |
| 10-13 years | 3,163 | 14.8% |
| 14+ years | 13,827 | 15.9% |
What the Sl 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.
- Suspension41 dangerous34.9%
- Tyres811 dangerous28%
- Brakes173 dangerous22%
- Lamps, reflectors and electrical equipment16 dangerous21.7%
- Noise, emissions and leaks7 dangerous12.7%
- Visibility3 dangerous11.9%
- Body, chassis, structure20 dangerous6%
- Steering6 dangerous4.5%
Is the Sl getting worse?
The fail rate rose 0.2 points to 14.9% from 2022 to 2025 while the median one tested aged 3 years, which is about what ageing alone predicts (0.2 points). Read it as the fleet getting older rather than the model changing.
| Year | Tests | Median age | Fail rate | All cars | |
|---|---|---|---|---|---|
| 2022 | 22,822 | 18 | 14.7% | 22.5% | |
| 2023 | 22,030 | 19 | 14.4% | 22.8% | |
| 2024 | 18,027 | 20 | 14.8% | 23.2% | |
| 2025 | 18,884 | 21 | 14.9% | 22.6% |
Fail rate is first attempts at class 4 tests. Median age is the age of a typical Sl 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 Sl in 2025, counted by how many tests each one appeared on.
- 1Ball joint: ball joint excessively worn260 tests
- 2Coil spring: fractured or broken239 tests
- 3Ball joint dust cover: ball joint dust cover no longer prevents the ingress of dirt230 tests
- 4Condition: has ply or cords exposed215 tests
- 5Condition: has a cut in excess of the requirements deep enough to reach the ply or cords211 tests
- 6Condition: has a tear, caused by separation or partial failure of its structure145 tests
- 7Rigid brake pipes: excessively corroded131 tests
- 8Wipers: does not clear the windscreen effectively129 tests
What wears out first
Advisories are the tester flagging wear that is still legal. A typical Sl collects 2.77 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.
- 1Rigid brake pipes: excessively corroded1,695 tests
- 2Tread depth: tread depth below requirements of 1.6mm1,570 tests
- 3Condition: has a tear, caused by separation or partial failure of its structure1,383 tests
- 4Engine oil leaks: leaking excessively from engine1,190 tests
- 5Brake discs: in such a condition that it is seriously weakened1,033 tests
- 6Ball joint: ball joint excessively worn817 tests
- 7Brake pads: less than 1.5 mm thick705 tests
- 8Wheel bearings: has excessive play509 tests
Questions
What is the Mercedes-Benz Sl MOT pass rate?
85.2% of the 19,227 Mercedes-Benz Sl first-attempt MOTs in 2025 passed. The fail rate of 14.8% compares with 22.6% across all cars. A further 2.4% passed after a defect was fixed during the test visit.
What does a Mercedes-Benz Sl usually fail on?
The single most common failure is "Ball joint: ball joint excessively worn", recorded on 260 failed tests, followed by "Coil spring: fractured or broken" and "Ball joint dust cover: ball joint dust cover no longer prevents the ingress of dirt". By section, suspension appears in 34.9% of failures, tyres appears in 28% of failures, brakes appears in 22% of failures.
Does age change the odds?
Sharply. At 3 to 5 years old the fail rate was 9.3%; at 14+ years it was 15.9%. The median Mercedes-Benz Sl tested in 2025 was 21 years old with 64,676 miles.
Is the Mercedes-Benz Sl getting less reliable?
The fail rate rose 0.2 points to 14.9% from 2022 to 2025 while the median one tested aged 3 years, which is about what ageing alone predicts (0.2 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 Sl 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 13 safety recalls naming the Mercedes-Benz Sl: Mercedes-Benz Sl recalls.
Other Mercedes-Benz models
Checking a particular Sl?
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.