2004 Mazda Rx-8 — MOT failures & pass rate
Across 3,496 MOT tests, the 2004 Mazda Rx-8 recorded a 75.7% pass rate. Against coupes & convertibles of a similar age (22.4% fail rate), the 2004 Rx-8 comes out 1.9pp worse. Failures cluster in emissions & environmental, suspension and lighting & signalling.
What the MOT record shows
No single area dominates — emissions & environmental (11.5%) and suspension (11.4%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are catalyst emissions, component mounting prescribed areas and malfunction indicator lamp — catalyst emissions alone was recorded 403 times.
Condition tracks the odometer closely. Failures run at 13.0% in the 0-30k band and 27.6% in the 120-150k band, a 14.6-point spread — more than double.
Brakes is the most common advisory, noted on 25.6% of tests — work that passed today but is likely due soon.
The trend is improving — the fail rate fell from 26.3% in 2021 to 21.7% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Emissions & environmental | 11.5% | 402 |
| 2 | Suspension | 11.4% | 397 |
| 3 | Lighting & signalling | 10.1% | 352 |
| 4 | Brakes | 7.8% | 273 |
| 5 | Body, structure & corrosion | 5.0% | 174 |
| 6 | Seat belts & restraints | 3.7% | 128 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Catalyst emissions | 403 |
| 2 | Component mounting prescribed areas | 301 |
| 3 | Malfunction indicator lamp | 202 |
| 4 | Headlamp aim | 183 |
| 5 | Service brake performance | 156 |
| 6 | Prescribed areas | 148 |
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 | 25.6% | 895 |
| 2 | Suspension | 24.2% | 845 |
| 3 | Tyres | 19.5% | 682 |
| 4 | Lighting & signalling | 11.2% | 390 |
| 5 | Body, structure & corrosion | 11.0% | 386 |
| 6 | Emissions & environmental | 10.5% | 368 |
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 | 261 | 13.0% |
| 30-60k | 1,153 | 22.6% |
| 60-90k | 1,505 | 26.8% |
| 90-120k | 474 | 25.5% |
| 120-150k | 87 | 27.6% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 986 | 26.3% |
| 2022 | 771 | 23.9% |
| 2023 | 679 | 23.0% |
| 2024 | 586 | 25.4% |
| 2025 | 474 | 21.7% |
What to check before buying a 2004 Rx-8
The failure pattern for this year is specific enough to inspect against: emissions & environmental accounted for 11.5% of tests. Start there.
- Emissions & environmental (11.5% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
- Suspension (11.4% 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.
- Lighting & signalling (10.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£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 2004 Mazda Rx-8s pass their MOT?
75.7% of the 3,496 2004 Mazda Rx-8 MOT tests in this dataset passed — a 24.3% fail rate.
What is the most common MOT failure on a 2004 Mazda Rx-8?
Emissions & environmental, recorded in 11.5% of tests, followed by suspension (11.4%).
Does the 2004 Rx-8 get worse with mileage?
Its MOT fail rate rises from 13.0% in the 0-30k band to 27.6% in the 120-150k band.
Methodology & source. Based on 3,496 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.