2018 Mercedes-Benz G-Class — MOT failures & pass rate
Across 1,498 MOT tests, the 2018 Mercedes-Benz G-Class recorded a 91.3% pass rate. Against large SUVs of a similar age (10.3% fail rate), the 2018 G-Class comes out 1.7pp better. Failures cluster in lighting & signalling, tyres and visibility.
What the MOT record shows
No single area dominates — lighting & signalling (3.4%) and tyres (3.0%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, registration plates and drag link end — headlamp aim alone was recorded 39 times.
Mileage is the strongest signal on the record: 5.9% of 0-30k cars fail, rising to 16.2% once past 60-90k — 2.8× the risk.
Advisories point at the next bill rather than this one: tyres was flagged on 11.4% of tests without failing them.
The trend is worsening — 6.8% of tests failed in 2021 against 11.6% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 3.4% | 51 |
| 2 | Tyres | 3.0% | 45 |
| 3 | Visibility | 1.3% | 20 |
| 4 | Steering | 1.1% | 17 |
| 5 | Brakes | 1.1% | 16 |
| 6 | Suspension | 1.0% | 15 |
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 | 39 |
| 2 | Registration plates | 24 |
| 3 | Drag link end | 20 |
| 4 | Wipers | 16 |
| 5 | Position lamp | 14 |
| 6 | Individual direction indicators | 11 |
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 | 11.4% | 171 |
| 2 | Brakes | 7.3% | 109 |
| 3 | Other defects | 5.1% | 76 |
| 4 | Steering | 3.1% | 46 |
| 5 | Visibility | 2.8% | 42 |
| 6 | Suspension | 2.1% | 31 |
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 | 680 | 5.9% |
| 30-60k | 654 | 9.8% |
| 60-90k | 136 | 16.2% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 1,013 | 7.2% |
| Diesel | 485 | 11.8% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 296 | 6.8% |
| 2022 | 306 | 7.5% |
| 2023 | 291 | 7.2% |
| 2024 | 302 | 10.3% |
| 2025 | 303 | 11.6% |
What to check before buying a 2018 G-Class
On a 2018 G-Class, lighting & signalling is what the MOT record says goes wrong most — it appeared in 3.4% of tests. Check these areas before you commit.
- Lighting & signalling (3.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Tyres (3.0% 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 (1.3% 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.
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 G-Classs pass their MOT?
91.3% of the 1,498 2018 Mercedes-Benz G-Class MOT tests in this dataset passed — a 8.7% fail rate.
What is the most common MOT failure on a 2018 Mercedes-Benz G-Class?
Lighting & signalling, recorded in 3.4% of tests, followed by tyres (3.0%).
Does the 2018 G-Class get worse with mileage?
Its MOT fail rate rises from 5.9% in the 0-30k band to 16.2% in the 60-90k band.
Methodology & source. Based on 1,498 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.