1989 Mercedes-Benz 300 — MOT failures & pass rate
Across 3,084 MOT tests, the 1989 Mercedes-Benz 300 recorded an 85.0% pass rate. That is 6.3 percentage points better than all cars of a similar age, which fail at 21.3%. Failures cluster in lighting & signalling, brakes and body, structure & corrosion.
What the MOT record shows
No single area dominates — lighting & signalling (8.0%) and brakes (5.4%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, service brake performance and washers — headlamp aim alone was recorded 145 times.
Condition tracks the odometer closely. Failures run at 11.2% in the 0-30k band and 24.0% in the 150k+ band, a 12.9-point spread — more than double.
Brakes is the most common advisory, noted on 19.9% of tests — work that passed today but is likely due soon.
The trend is improving — the fail rate fell from 17.2% in 2021 to 14.9% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 8.0% | 247 |
| 2 | Brakes | 5.4% | 167 |
| 3 | Body, structure & corrosion | 4.4% | 135 |
| 4 | Visibility | 4.0% | 124 |
| 5 | Suspension | 4.0% | 124 |
| 6 | Emissions & environmental | 2.9% | 89 |
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 | 145 |
| 2 | Service brake performance | 105 |
| 3 | Washers | 89 |
| 4 | Wipers | 69 |
| 5 | Non catalyst emissions | 61 |
| 6 | Headlamp | 54 |
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 | 19.9% | 615 |
| 2 | Suspension | 19.7% | 606 |
| 3 | Emissions & environmental | 14.6% | 451 |
| 4 | Tyres | 12.1% | 372 |
| 5 | Body, structure & corrosion | 11.0% | 339 |
| 6 | Steering | 9.6% | 297 |
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 | 188 | 11.2% |
| 30-60k | 514 | 9.9% |
| 60-90k | 756 | 13.4% |
| 90-120k | 618 | 14.4% |
| 120-150k | 538 | 16.2% |
| 150k+ | 470 | 24.0% |
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 2,854 | 14.5% |
| Diesel | 230 | 21.3% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 670 | 17.2% |
| 2022 | 631 | 13.5% |
| 2023 | 603 | 15.6% |
| 2024 | 597 | 13.6% |
| 2025 | 583 | 14.9% |
What to check before buying a 1989 300
The failure pattern for this year is specific enough to inspect against: lighting & signalling accounted for 8.0% of tests. Start there.
- Lighting & signalling (8.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (5.4% 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 (4.4% 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 1989 Mercedes-Benz 300s pass their MOT?
85.0% of the 3,084 1989 Mercedes-Benz 300 MOT tests in this dataset passed — a 15.0% fail rate.
What is the most common MOT failure on a 1989 Mercedes-Benz 300?
Lighting & signalling, recorded in 8.0% of tests, followed by brakes (5.4%).
Does the 1989 300 get worse with mileage?
Its MOT fail rate rises from 11.2% in the 0-30k band to 24.0% in the 150k+ band.
Methodology & source. Based on 3,084 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.