2018 SEAT Mii — MOT failures & pass rate
The 2018 SEAT Mii passed 91.5% of its 6,876 recorded MOT tests. That is 2.6 percentage points better than all cars of a similar age, which fail at 11.1%. Failures cluster in visibility, lighting & signalling and tyres.
What the MOT record shows
No single area dominates — visibility (4.7%) and lighting & signalling (4.6%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are wipers, headlamp aim and tread depth — wipers alone was recorded 320 times.
Mileage is the strongest signal on the record: 6.4% of 0-30k cars fail, rising to 21.7% once past 90-120k — 3.4× the risk.
Advisories point at the next bill rather than this one: tyres was flagged on 21.7% of tests without failing them.
The trend is worsening — 4.7% of tests failed in 2021 against 11.5% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Visibility | 4.7% | 322 |
| 2 | Lighting & signalling | 4.6% | 314 |
| 3 | Tyres | 3.1% | 212 |
| 4 | Brakes | 1.8% | 126 |
| 5 | Suspension | 1.0% | 71 |
| 6 | Emissions & environmental | 0.7% | 45 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Wipers | 320 |
| 2 | Headlamp aim | 238 |
| 3 | Tread depth | 88 |
| 4 | Position lamp | 80 |
| 5 | Washers | 78 |
| 6 | Catalyst emissions | 75 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 21.7% | 1,489 |
| 2 | Brakes | 8.7% | 596 |
| 3 | Other defects | 5.5% | 379 |
| 4 | Suspension | 3.9% | 266 |
| 5 | Visibility | 3.0% | 204 |
| 6 | Road wheels | 0.5% | 33 |
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 | 4,368 | 6.4% |
| 30-60k | 2,153 | 11.2% |
| 60-90k | 296 | 17.2% |
| 90-120k | 46 | 21.7% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,347 | 4.7% |
| 2022 | 1,363 | 7.3% |
| 2023 | 1,373 | 8.3% |
| 2024 | 1,380 | 10.6% |
| 2025 | 1,413 | 11.5% |
What to check before buying a 2018 Mii
On a 2018 Mii, visibility is what the MOT record says goes wrong most — it appeared in 4.7% of tests. Check these areas before you commit.
- Visibility (4.7% 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.
- Lighting & signalling (4.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Tyres (3.1% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
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 2018 SEAT Miis pass their MOT?
91.5% of the 6,876 2018 SEAT Mii MOT tests in this dataset passed — a 8.5% fail rate.
What is the most common MOT failure on a 2018 SEAT Mii?
Visibility, recorded in 4.7% of tests, followed by lighting & signalling (4.6%).
Does the 2018 Mii get worse with mileage?
Its MOT fail rate rises from 6.4% in the 0-30k band to 21.7% in the 90-120k band.
Methodology & source. Based on 6,876 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.