Porsche 928 S MOT pass rate & common failures
Across 40 model years and 3,146 tests, the Porsche 928 S passes its MOT 82.6% of the time. All cars of a similar age fail 20.8% of the time, so this is 3.5pp better than the group it competes with. Its most common failure areas are lighting & signalling, visibility and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 12.1% of all tests — 6.2 points clear of visibility, so it is the first thing to check.
At component level the recurring items are headlamp aim, washers and rear fog lamp — headlamp aim alone was recorded 215 times.
Mileage matters less than usual here: the 928 S fails 17.7% of the time in the 0-30k band and 15.3% at 150k+, a spread of only 2.4 points.
Advisories point at the next bill rather than this one: emissions & environmental was flagged on 19.1% of tests without failing them.
The trend is improving — the fail rate fell from 19.4% in 2021 to 15.2% in 2025, as the worst-kept examples leave the fleet.
How it compares
By model year
Every 928 S model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 1982 | 64 | 87.5% | 12.5% | Brakes |
| 1983 | 123 | 80.5% | 19.5% | Lighting & signalling |
| 1984 | 249 | 83.5% | 16.5% | Lighting & signalling |
| 1985 | 245 | 77.5% | 22.4% | Lighting & signalling |
| 1986 | 396 | 81.3% | 18.7% | Lighting & signalling |
| 1987 | 344 | 83.1% | 16.9% | Lighting & signalling |
| 1988 | 513 | 85.4% | 14.6% | Lighting & signalling |
| 1989 | 440 | 81.8% | 18.2% | Lighting & signalling |
| 1990 | 263 | 82.9% | 17.1% | Lighting & signalling |
| 1991 | 275 | 84.0% | 16.0% | Lighting & signalling |
| 1992 | 102 | 81.4% | 18.6% | Lighting & signalling |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 12.1% | 380 |
| 2 | Visibility | 5.9% | 186 |
| 3 | Brakes | 4.5% | 143 |
| 4 | Body, structure & corrosion | 3.7% | 117 |
| 5 | Emissions & environmental | 3.7% | 116 |
| 6 | Suspension | 2.8% | 87 |
| 7 | Steering | 2.7% | 84 |
| 8 | Tyres | 1.4% | 44 |
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 | 215 |
| 2 | Washers | 162 |
| 3 | Rear fog lamp | 132 |
| 4 | Non catalyst emissions | 70 |
| 5 | Position lamp | 68 |
| 6 | Service brake performance | 67 |
| 7 | Headlamp | 67 |
| 8 | Joints | 67 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Emissions & environmental | 19.1% | 601 |
| 2 | Suspension | 16.7% | 524 |
| 3 | Other defects | 12.3% | 388 |
| 4 | Brakes | 12.0% | 378 |
| 5 | Tyres | 9.8% | 309 |
| 6 | Body, structure & corrosion | 6.6% | 209 |
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 | 124 | 17.7% |
| 30-60k | 248 | 15.7% |
| 60-90k | 520 | 17.1% |
| 90-120k | 999 | 17.5% |
| 120-150k | 822 | 18.4% |
| 150k+ | 418 | 15.3% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 706 | 19.4% |
| 2022 | 697 | 18.8% |
| 2023 | 654 | 16.5% |
| 2024 | 575 | 16.0% |
| 2025 | 514 | 15.2% |
What to check before buying a Porsche 928 S
- Lighting & signalling (12.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Visibility (5.9% 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.
- Brakes (4.5% 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
What is the MOT pass rate for the Porsche 928 S?
82.6% of the 3,146 Porsche 928 S MOT tests in this dataset passed, a 17.4% fail rate, across model years 1980–2019.
What does the Porsche 928 S most often fail its MOT on?
Lighting & signalling, recorded in 12.1% of tests, then visibility (5.9%).
How much does mileage affect 928 S MOT results?
Fail rates run at 17.7% for cars in the 0-30k band and 15.3% for 150k+, a 2.4-point difference.
Methodology & source. Based on 3,146 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.