Porsche 928 MOT pass rate & common failures
The Porsche 928 appears in 1,066 MOT tests spanning model years 1980–2020, and 85.5% of them passed. That is 7.9 percentage points better than all cars of a similar age, which fail at 22.4%. Its most common failure areas are lighting & signalling, emissions & environmental and visibility.
What the MOT record shows
No single area dominates — lighting & signalling (9.0%) and emissions & environmental (7.2%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are catalyst emissions, headlamp aim and rear fog lamp — catalyst emissions alone was recorded 88 times.
Mileage is the strongest signal on the record: 12.3% of 0-30k cars fail, rising to 19.4% once past 150k.
Advisories point at the next bill rather than this one: suspension was flagged on 9.9% of tests without failing them.
The trend is improving — the fail rate fell from 16.3% in 2021 to 12.1% in 2025, as the worst-kept examples leave the fleet.
How it compares
By model year
Every 928 model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 1989 | 167 | 85.6% | 14.4% | Lighting & signalling |
| 1990 | 124 | 88.7% | 11.3% | Lighting & signalling |
| 1991 | 85 | 89.4% | 10.6% | Lighting & signalling |
| 1992 | 77 | 89.6% | 10.4% | Lighting & signalling |
| 1993 | 127 | 85.0% | 15.0% | Lighting & signalling |
| 1994 | 175 | 82.9% | 17.1% | Emissions & environmental |
| 1995 | 181 | 82.9% | 17.1% | Emissions & environmental |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 9.0% | 96 |
| 2 | Emissions & environmental | 7.2% | 77 |
| 3 | Visibility | 3.0% | 32 |
| 4 | Brakes | 2.6% | 28 |
| 5 | Steering | 1.7% | 18 |
| 6 | Body, structure & corrosion | 1.3% | 14 |
| 7 | Seat belts & restraints | 1.2% | 13 |
| 8 | Suspension | 0.9% | 10 |
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 | 88 |
| 2 | Headlamp aim | 61 |
| 3 | Rear fog lamp | 27 |
| 4 | Washers | 26 |
| 5 | Headlamp | 20 |
| 6 | Wipers | 12 |
| 7 | Steering rack | 12 |
| 8 | Flexible brake hoses | 12 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Suspension | 9.9% | 106 |
| 2 | Brakes | 9.2% | 98 |
| 3 | Other defects | 9.0% | 96 |
| 4 | Emissions & environmental | 8.9% | 95 |
| 5 | Tyres | 8.1% | 86 |
| 6 | Body, structure & corrosion | 3.4% | 36 |
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 | 73 | 12.3% |
| 30-60k | 148 | 18.2% |
| 60-90k | 245 | 16.7% |
| 90-120k | 298 | 9.4% |
| 120-150k | 165 | 14.5% |
| 150k+ | 134 | 19.4% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 246 | 16.3% |
| 2022 | 219 | 16.0% |
| 2023 | 206 | 14.1% |
| 2024 | 205 | 13.7% |
| 2025 | 190 | 12.1% |
What to check before buying a Porsche 928
- Lighting & signalling (9.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (7.2% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
- Visibility (3.0% 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
What is the MOT pass rate for the Porsche 928?
85.5% of the 1,066 Porsche 928 MOT tests in this dataset passed, a 14.5% fail rate, across model years 1980–2020.
What does the Porsche 928 most often fail its MOT on?
Lighting & signalling, recorded in 9.0% of tests, then emissions & environmental (7.2%).
How much does mileage affect 928 MOT results?
Fail rates run at 12.3% for cars in the 0-30k band and 19.4% for 150k+, a 7.1-point difference.
Methodology & source. Based on 1,066 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.