2018 Mercedes-Benz GLS — MOT failures & pass rate
3,296 MOT tests on the 2018 Mercedes-Benz GLS are in this dataset, and 89.9% of them passed. Large SUVs of a similar age fail at 10.3%, so the 2018 GLS sits squarely on the average. Failures cluster in tyres, brakes and body, structure & corrosion.
What the MOT record shows
Tyres dominates the failure mix at 6.7% of all tests — 5.1 points clear of brakes, so it is the first thing to check.
At component level the recurring items are tread depth, brake pads and registration plates — tread depth alone was recorded 147 times.
Mileage is the strongest signal on the record: 7.5% of 0-30k cars fail, rising to 14.2% once past 90-120k.
Advisories point at the next bill rather than this one: tyres was flagged on 19.8% of tests without failing them.
The trend is worsening — 9.5% of tests failed in 2021 against 11.5% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.7% | 222 |
| 2 | Brakes | 1.6% | 54 |
| 3 | Body, structure & corrosion | 1.1% | 37 |
| 4 | Lighting & signalling | 1.0% | 34 |
| 5 | Other defects | 0.9% | 29 |
| 6 | Emissions & environmental | 0.6% | 21 |
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 | 147 |
| 2 | Brake pads | 60 |
| 3 | Registration plates | 48 |
| 4 | Joints | 30 |
| 5 | Headlamp aim | 28 |
| 6 | Malfunction indicator lamp | 18 |
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 | 19.8% | 653 |
| 2 | Brakes | 9.9% | 327 |
| 3 | Other defects | 5.8% | 191 |
| 4 | Body, structure & corrosion | 3.5% | 116 |
| 5 | Visibility | 3.2% | 106 |
| 6 | Emissions & environmental | 0.9% | 28 |
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 | 944 | 7.5% |
| 30-60k | 1,618 | 10.1% |
| 60-90k | 571 | 13.7% |
| 90-120k | 127 | 14.2% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 2,902 | 10.5% |
| Petrol | 394 | 7.1% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 707 | 9.5% |
| 2022 | 676 | 8.4% |
| 2023 | 651 | 9.8% |
| 2024 | 645 | 11.5% |
| 2025 | 617 | 11.5% |
What to check before buying a 2018 GLS
On a 2018 GLS, tyres is what the MOT record says goes wrong most — it appeared in 6.7% of tests. Check these areas before you commit.
- Tyres (6.7% 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.
- Brakes (1.6% 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.
- Body, structure & corrosion (1.1% of tests): The one to take seriously on older cars — corrosion to structural areas can be costly and is an MOT failure. Typical repair: £200–£1,500+.
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 GLSs pass their MOT?
89.9% of the 3,296 2018 Mercedes-Benz GLS MOT tests in this dataset passed — a 10.1% fail rate.
What is the most common MOT failure on a 2018 Mercedes-Benz GLS?
Tyres, recorded in 6.7% of tests, followed by brakes (1.6%).
Does the 2018 GLS get worse with mileage?
Its MOT fail rate rises from 7.5% in the 0-30k band to 14.2% in the 90-120k band.
Methodology & source. Based on 3,296 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.