1988 Porsche 928 S — MOT failures & pass rate
Across 513 MOT tests, the 1988 Porsche 928 S recorded an 85.4% pass rate. All cars of a similar age fail 20.9% of the time, so this is 6.3pp better than the group it competes with. Failures cluster in lighting & signalling, emissions & environmental and body, structure & corrosion.
What the MOT record shows
Lighting & signalling dominates the failure mix at 8.6% of all tests — 4.5 points clear of emissions & environmental, so it is the first thing to check.
At component level the recurring items are headlamp aim, joints and non catalyst emissions — headlamp aim alone was recorded 22 times.
Condition tracks the odometer closely. Failures run at 8.0% in the 30-60k band and 14.3% in the 150k+ band, a 6.3-point spread.
Advisories point at the next bill rather than this one: emissions & environmental was flagged on 17.5% of tests without failing them.
The trend is improving — the fail rate fell from 21.3% in 2021 to 13.3% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 8.6% | 44 |
| 2 | Emissions & environmental | 4.1% | 21 |
| 3 | Body, structure & corrosion | 3.7% | 19 |
| 4 | Visibility | 3.1% | 16 |
| 5 | Brakes | 2.5% | 13 |
| 6 | Suspension | 2.1% | 11 |
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 | 22 |
| 2 | Joints | 17 |
| 3 | Non catalyst emissions | 16 |
| 4 | Rear fog lamp | 16 |
| 5 | Headlamp | 15 |
| 6 | Washers | 13 |
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 | 17.5% | 90 |
| 2 | Suspension | 12.3% | 63 |
| 3 | Brakes | 10.7% | 55 |
| 4 | Tyres | 10.1% | 52 |
| 5 | Other defects | 8.2% | 42 |
| 6 | Body, structure & corrosion | 8.0% | 41 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 30-60k | 50 | 8.0% |
| 60-90k | 79 | 15.2% |
| 90-120k | 149 | 14.1% |
| 120-150k | 172 | 16.9% |
| 150k+ | 49 | 14.3% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 108 | 21.3% |
| 2022 | 112 | 15.2% |
| 2023 | 104 | 10.6% |
| 2024 | 91 | 12.1% |
| 2025 | 98 | 13.3% |
What to check before buying a 1988 928 S
On a 1988 928 S, lighting & signalling is what the MOT record says goes wrong most — it appeared in 8.6% of tests. Check these areas before you commit.
- Lighting & signalling (8.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (4.1% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
- Body, structure & corrosion (3.7% 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 1988 Porsche 928 Ss pass their MOT?
85.4% of the 513 1988 Porsche 928 S MOT tests in this dataset passed — a 14.6% fail rate.
What is the most common MOT failure on a 1988 Porsche 928 S?
Lighting & signalling, recorded in 8.6% of tests, followed by emissions & environmental (4.1%).
Does the 1988 928 S get worse with mileage?
Its MOT fail rate rises from 8.0% in the 30-60k band to 14.3% in the 150k+ band.
Methodology & source. Based on 513 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.