2018 Mercedes-Benz A-Class — MOT failures & pass rate
The 2018 Mercedes-Benz A-Class passed 89.4% of its 230,140 recorded MOT tests. Small family cars of a similar age fail at 10.4%, so the 2018 A-Class sits squarely on the average. Failures cluster in tyres, visibility and brakes.
What the MOT record shows
Tyres dominates the failure mix at 5.8% of all tests — 3.5 points clear of visibility, so it is the first thing to check.
At component level the recurring items are tread depth, brake pads and headlamp aim — tread depth alone was recorded 6,568 times.
A 150k+ example is materially riskier than a 0-30k one: 20.9% versus 7.3%.
Split by fuel, diesel examples fail 1.6pp more often than petrol ones (11.4% vs 9.8%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: tyres was flagged on 24.8% of tests without failing them.
The trend is worsening — 8.1% of tests failed in 2021 against 12.8% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.8% | 13,261 |
| 2 | Visibility | 2.3% | 5,181 |
| 3 | Brakes | 2.2% | 5,011 |
| 4 | Lighting & signalling | 1.9% | 4,482 |
| 5 | Seat belts & restraints | 1.5% | 3,381 |
| 6 | Emissions & environmental | 0.9% | 2,038 |
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 | 6,568 |
| 2 | Brake pads | 4,793 |
| 3 | Headlamp aim | 3,749 |
| 4 | Washers | 3,107 |
| 5 | SRS malfunction indicator lamp | 3,105 |
| 6 | Wipers | 2,624 |
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 | 24.8% | 57,158 |
| 2 | Brakes | 13.8% | 31,743 |
| 3 | Other defects | 5.7% | 13,103 |
| 4 | Visibility | 3.2% | 7,265 |
| 5 | Suspension | 1.4% | 3,290 |
| 6 | Road wheels | 0.8% | 1,879 |
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 | 80,716 | 7.3% |
| 30-60k | 111,569 | 11.5% |
| 60-90k | 32,202 | 14.6% |
| 90-120k | 4,852 | 15.3% |
| 120-150k | 615 | 18.2% |
| 150k+ | 148 | 20.9% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 115,651 | 11.4% |
| Petrol | 114,489 | 9.8% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 45,648 | 8.1% |
| 2022 | 45,758 | 9.0% |
| 2023 | 45,974 | 10.8% |
| 2024 | 46,182 | 12.2% |
| 2025 | 46,578 | 12.8% |
What to check before buying a 2018 A-Class
On a 2018 A-Class, tyres is what the MOT record says goes wrong most — it appeared in 5.8% of tests. Check these areas before you commit.
- Tyres (5.8% 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.
- Visibility (2.3% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£150.
- Brakes (2.2% 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.
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 A-Classs pass their MOT?
89.4% of the 230,140 2018 Mercedes-Benz A-Class MOT tests in this dataset passed — a 10.6% fail rate.
What is the most common MOT failure on a 2018 Mercedes-Benz A-Class?
Tyres, recorded in 5.8% of tests, followed by visibility (2.3%).
Does the 2018 A-Class get worse with mileage?
Its MOT fail rate rises from 7.3% in the 0-30k band to 20.9% in the 150k+ band.
Methodology & source. Based on 230,140 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.