2018 Mercedes-Benz X — MOT failures & pass rate
Across 7,292 MOT tests, the 2018 Mercedes-Benz X recorded an 85.1% pass rate. Against all cars of a similar age (11.0% fail rate), the 2018 X comes out 3.9pp worse. Failures cluster in brakes, lighting & signalling and emissions & environmental.
What the MOT record shows
No single area dominates — brakes (6.2%) and lighting & signalling (4.2%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are malfunction indicator lamp, brake pads and wipers — malfunction indicator lamp alone was recorded 288 times.
A 150k+ example is materially riskier than a 0-30k one: 23.3% versus 9.8%.
Advisories point at the next bill rather than this one: brakes was flagged on 17.0% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Brakes | 6.2% | 452 |
| 2 | Lighting & signalling | 4.2% | 303 |
| 3 | Emissions & environmental | 4.1% | 300 |
| 4 | Tyres | 3.7% | 271 |
| 5 | Visibility | 2.9% | 211 |
| 6 | Seat belts & restraints | 2.3% | 167 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Malfunction indicator lamp | 288 |
| 2 | Brake pads | 239 |
| 3 | Wipers | 182 |
| 4 | Tread depth | 178 |
| 5 | Rbt (sp) | 150 |
| 6 | SRS malfunction indicator lamp | 146 |
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 | 17.0% | 1,242 |
| 2 | Tyres | 16.1% | 1,174 |
| 3 | Visibility | 5.1% | 373 |
| 4 | Lighting & signalling | 5.0% | 362 |
| 5 | Suspension | 4.9% | 354 |
| 6 | Other defects | 4.3% | 314 |
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 | 1,156 | 9.8% |
| 30-60k | 3,165 | 14.6% |
| 60-90k | 1,949 | 16.3% |
| 90-120k | 691 | 18.5% |
| 120-150k | 211 | 18.0% |
| 150k+ | 116 | 23.3% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,382 | 13.9% |
| 2022 | 1,503 | 13.7% |
| 2023 | 1,482 | 16.0% |
| 2024 | 1,499 | 16.1% |
| 2025 | 1,426 | 14.8% |
What to check before buying a 2018 X
On a 2018 X, brakes is what the MOT record says goes wrong most — it appeared in 6.2% of tests. Check these areas before you commit.
- Brakes (6.2% 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.
- Lighting & signalling (4.2% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (4.1% 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 2018 Mercedes-Benz Xs pass their MOT?
85.1% of the 7,292 2018 Mercedes-Benz X MOT tests in this dataset passed — a 14.9% fail rate.
What is the most common MOT failure on a 2018 Mercedes-Benz X?
Brakes, recorded in 6.2% of tests, followed by lighting & signalling (4.2%).
Does the 2018 X get worse with mileage?
Its MOT fail rate rises from 9.8% in the 0-30k band to 23.3% in the 150k+ band.
Methodology & source. Based on 7,292 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.