1991 Mercedes-Benz 300 — MOT failures & pass rate
Across 2,333 MOT tests, the 1991 Mercedes-Benz 300 recorded an 81.2% pass rate. That is 3.6 percentage points better than all cars of a similar age, which fail at 22.4%. Failures cluster in lighting & signalling, suspension and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 12.0% of all tests — 5.3 points clear of suspension, so it is the first thing to check.
At component level the recurring items are headlamp aim, track rod end and headlamp — headlamp aim alone was recorded 117 times.
A 150k+ example is materially riskier than a 0-30k one: 22.7% versus 10.9%.
Split by fuel, diesel examples fail 5.2pp more often than petrol ones (22.9% vs 17.7%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: brakes was flagged on 26.8% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 12.0% | 281 |
| 2 | Suspension | 6.8% | 158 |
| 3 | Brakes | 6.7% | 156 |
| 4 | Body, structure & corrosion | 5.4% | 125 |
| 5 | Visibility | 3.8% | 88 |
| 6 | Steering | 2.9% | 68 |
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 | 117 |
| 2 | Track rod end | 70 |
| 3 | Headlamp | 63 |
| 4 | Position lamp | 58 |
| 5 | Rigid brake pipes | 53 |
| 6 | Exhaust system | 50 |
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 | 26.8% | 624 |
| 2 | Suspension | 26.6% | 620 |
| 3 | Emissions & environmental | 19.6% | 457 |
| 4 | Tyres | 14.5% | 338 |
| 5 | Body, structure & corrosion | 10.9% | 254 |
| 6 | Steering | 9.9% | 232 |
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 | 55 | 10.9% |
| 30-60k | 148 | 12.2% |
| 60-90k | 351 | 16.2% |
| 90-120k | 467 | 16.1% |
| 120-150k | 435 | 19.3% |
| 150k+ | 877 | 22.7% |
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 1,817 | 17.7% |
| Diesel | 516 | 22.9% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 571 | 18.6% |
| 2022 | 501 | 18.6% |
| 2023 | 464 | 19.0% |
| 2024 | 414 | 19.8% |
| 2025 | 383 | 18.3% |
What to check before buying a 1991 300
On a 1991 300, lighting & signalling is what the MOT record says goes wrong most — it appeared in 12.0% of tests. Check these areas before you commit.
- Lighting & signalling (12.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (6.8% 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.
- Brakes (6.7% 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 1991 Mercedes-Benz 300s pass their MOT?
81.2% of the 2,333 1991 Mercedes-Benz 300 MOT tests in this dataset passed — a 18.8% fail rate.
What is the most common MOT failure on a 1991 Mercedes-Benz 300?
Lighting & signalling, recorded in 12.0% of tests, followed by suspension (6.8%).
Does the 1991 300 get worse with mileage?
Its MOT fail rate rises from 10.9% in the 0-30k band to 22.7% in the 150k+ band.
Methodology & source. Based on 2,333 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.