2012 Mercedes-Benz S-Class — MOT failures & pass rate
Across 7,423 MOT tests, the 2012 Mercedes-Benz S-Class recorded an 84.2% pass rate. That is 2.5 percentage points better than executive cars of a similar age, which fail at 18.3%. Failures cluster in brakes, suspension and emissions & environmental.
What the MOT record shows
No single area dominates — brakes (6.3%) and suspension (5.6%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are ball joint, malfunction indicator lamp and tread depth — ball joint alone was recorded 342 times.
Mileage is the strongest signal on the record: 5.2% of 0-30k cars fail, rising to 15.2% once past 150k — 2.9× the risk.
Split by fuel, diesel examples fail 2.6pp more often than petrol ones (16.1% vs 13.5%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: brakes was flagged on 27.2% of tests without failing them.
The trend is improving — the fail rate fell from 16.0% in 2021 to 14.0% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Brakes | 6.3% | 467 |
| 2 | Suspension | 5.6% | 416 |
| 3 | Emissions & environmental | 4.8% | 359 |
| 4 | Tyres | 4.8% | 359 |
| 5 | Lighting & signalling | 2.6% | 192 |
| 6 | Visibility | 1.7% | 126 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Ball joint | 342 |
| 2 | Malfunction indicator lamp | 326 |
| 3 | Tread depth | 243 |
| 4 | Rbt (sp) | 218 |
| 5 | Rigid brake pipes | 149 |
| 6 | Headlamp aim | 121 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 27.2% | 2,019 |
| 2 | Tyres | 23.6% | 1,752 |
| 3 | Suspension | 17.9% | 1,327 |
| 4 | Emissions & environmental | 7.1% | 528 |
| 5 | Other defects | 4.9% | 360 |
| 6 | Visibility | 3.7% | 275 |
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 | 155 | 5.2% |
| 30-60k | 1,238 | 15.3% |
| 60-90k | 2,329 | 16.8% |
| 90-120k | 1,700 | 15.6% |
| 120-150k | 1,077 | 17.0% |
| 150k+ | 920 | 15.2% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 6,687 | 16.1% |
| Petrol | 735 | 13.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,597 | 16.0% |
| 2022 | 1,591 | 16.3% |
| 2023 | 1,498 | 16.8% |
| 2024 | 1,433 | 15.9% |
| 2025 | 1,304 | 14.0% |
What to check before buying a 2012 S-Class
On a 2012 S-Class, brakes is what the MOT record says goes wrong most — it appeared in 6.3% of tests. Check these areas before you commit.
- Brakes (6.3% 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.
- Suspension (5.6% 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.
- Emissions & environmental (4.8% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
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 2012 Mercedes-Benz S-Classs pass their MOT?
84.2% of the 7,423 2012 Mercedes-Benz S-Class MOT tests in this dataset passed — a 15.8% fail rate.
What is the most common MOT failure on a 2012 Mercedes-Benz S-Class?
Brakes, recorded in 6.3% of tests, followed by suspension (5.6%).
Does the 2012 S-Class get worse with mileage?
Its MOT fail rate rises from 5.2% in the 0-30k band to 15.2% in the 150k+ band.
Methodology & source. Based on 7,423 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.