2018 Mercedes-Benz SLC — MOT failures & pass rate
The 2018 Mercedes-Benz SLC passed 92.2% of its 8,161 recorded MOT tests. Against coupes & convertibles of a similar age (9.1% fail rate), the 2018 SLC comes out 1.2pp better. Failures cluster in tyres, lighting & signalling and suspension.
What the MOT record shows
Tyres dominates the failure mix at 5.2% of all tests — 3.6 points clear of lighting & signalling, so it is the first thing to check.
At component level the recurring items are headlamp aim, tread depth and registration plates — headlamp aim alone was recorded 116 times.
A 90-120k example is materially riskier than a 0-30k one: 21.9% versus 5.8%.
Split by fuel, diesel examples fail 3.6pp more often than petrol ones (11.0% vs 7.4%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: tyres was flagged on 23.1% of tests without failing them.
The trend is worsening — 6.3% of tests failed in 2021 against 9.1% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.2% | 428 |
| 2 | Lighting & signalling | 1.6% | 133 |
| 3 | Suspension | 0.9% | 73 |
| 4 | Brakes | 0.7% | 59 |
| 5 | Emissions & environmental | 0.7% | 55 |
| 6 | Visibility | 0.6% | 46 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 116 |
| 2 | Tread depth | 97 |
| 3 | Registration plates | 42 |
| 4 | Catalyst emissions | 30 |
| 5 | Washers | 30 |
| 6 | Malfunction indicator lamp | 24 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 23.1% | 1,882 |
| 2 | Brakes | 3.4% | 280 |
| 3 | Suspension | 2.9% | 235 |
| 4 | Other defects | 2.6% | 216 |
| 5 | Visibility | 1.7% | 137 |
| 6 | Road wheels | 1.5% | 124 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 5,843 | 5.8% |
| 30-60k | 2,085 | 12.2% |
| 60-90k | 191 | 18.3% |
| 90-120k | 32 | 21.9% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 7,185 | 7.4% |
| Diesel | 976 | 11.0% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,667 | 6.3% |
| 2022 | 1,649 | 6.6% |
| 2023 | 1,629 | 7.8% |
| 2024 | 1,594 | 9.5% |
| 2025 | 1,622 | 9.1% |
What to check before buying a 2018 SLC
On a 2018 SLC, tyres is what the MOT record says goes wrong most — it appeared in 5.2% of tests. Check these areas before you commit.
- Tyres (5.2% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (1.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (0.9% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2018 Mercedes-Benz SLCs pass their MOT?
92.2% of the 8,161 2018 Mercedes-Benz SLC MOT tests in this dataset passed — a 7.8% fail rate.
What is the most common MOT failure on a 2018 Mercedes-Benz SLC?
Tyres, recorded in 5.2% of tests, followed by lighting & signalling (1.6%).
Does the 2018 SLC get worse with mileage?
Its MOT fail rate rises from 5.8% in the 0-30k band to 21.9% in the 90-120k band.
Methodology & source. Based on 8,161 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.