2018 Mercedes-Benz S-Class — MOT failures & pass rate
The 2018 Mercedes-Benz S-Class passed 93.2% of its 13,170 recorded MOT tests. Against executive cars of a similar age (10.8% fail rate), the 2018 S-Class comes out 3.9pp better. Failures cluster in tyres, suspension and brakes.
What the MOT record shows
No single area dominates — tyres (3.9%) and suspension (1.1%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are tread depth, ball joint and brake pads — tread depth alone was recorded 286 times.
Mileage matters less than usual here: the 2018 S-Class fails 6.4% of the time in the 0-30k band and 7.5% at 150k+, a spread of only 1.2 points.
Fuel type barely separates them — diesel fails 6.7% of the time against 7.2% for petrol.
Advisories point at the next bill rather than this one: tyres was flagged on 15.5% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 3.9% | 518 |
| 2 | Suspension | 1.1% | 143 |
| 3 | Brakes | 0.9% | 118 |
| 4 | Visibility | 0.9% | 117 |
| 5 | Lighting & signalling | 0.8% | 110 |
| 6 | Emissions & environmental | 0.8% | 105 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Tread depth | 286 |
| 2 | Ball joint | 150 |
| 3 | Brake pads | 129 |
| 4 | Registration plates | 121 |
| 5 | Headlamp aim | 99 |
| 6 | Malfunction indicator lamp | 95 |
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 | 15.5% | 2,039 |
| 2 | Brakes | 8.7% | 1,144 |
| 3 | Suspension | 2.9% | 375 |
| 4 | Other defects | 2.6% | 344 |
| 5 | Visibility | 2.4% | 310 |
| 6 | Road wheels | 0.7% | 92 |
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 | 3,662 | 6.4% |
| 30-60k | 4,555 | 7.8% |
| 60-90k | 2,455 | 6.7% |
| 90-120k | 1,276 | 4.9% |
| 120-150k | 672 | 5.8% |
| 150k+ | 544 | 7.5% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 9,785 | 6.7% |
| Petrol | 3,344 | 7.2% |
| Hybrid | 41 | 4.9% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 2,783 | 6.2% |
| 2022 | 2,871 | 5.8% |
| 2023 | 2,688 | 6.9% |
| 2024 | 2,516 | 8.1% |
| 2025 | 2,312 | 7.4% |
What to check before buying a 2018 S-Class
On a 2018 S-Class, tyres is what the MOT record says goes wrong most — it appeared in 3.9% of tests. Check these areas before you commit.
- Tyres (3.9% 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.
- Suspension (1.1% 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.
- Brakes (0.9% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
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 S-Classs pass their MOT?
93.2% of the 13,170 2018 Mercedes-Benz S-Class MOT tests in this dataset passed — a 6.8% fail rate.
What is the most common MOT failure on a 2018 Mercedes-Benz S-Class?
Tyres, recorded in 3.9% of tests, followed by suspension (1.1%).
Does the 2018 S-Class get worse with mileage?
Its MOT fail rate rises from 6.4% in the 0-30k band to 7.5% in the 150k+ band.
Methodology & source. Based on 13,170 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.