15,927 tests in 2025
SEAT Mii reliability and MOT pass rate
80.9% passed first time. The 19.1% fail rate is 3.5 points better than the all-car average, on a median example 10 years old with 53,343 miles.
Petrol, diesel and hybrid versions. The electric version has its own page: SEAT Mii Electric.
Pass rate
80.9%
22.6% of all cars failed; 19.1% of these did.
Fixed on the day
5.9%
Passed after a defect was put right during the visit.
Median at test
53,343 mi
10 years old.
Fail rate by age
| Age at test | Tests | Fail rate |
|---|---|---|
| 3-5 years | 2 | — |
| 6-9 years | 5,776 | 15.9% |
| 10-13 years | 10,149 | 20.8% |
| 14+ years | 0 | — |
What the Mii fails on
Share of failed tests with at least one fail item in each DVSA inspection section. A test can fail in several sections at once.
- Brakes252 dangerous31.6%
- Lamps, reflectors and electrical equipment4 dangerous25.9%
- Suspension49 dangerous25.8%
- Tyres680 dangerous20.5%
- Noise, emissions and leaks1 dangerous14.4%
- Body, chassis, structure34 dangerous13.1%
- Visibility1 dangerous10.9%
- Seat belts and supplementary restraint systems7.9%
Is the Mii getting worse?
The fail rate rose 6.1 points to 19.1% from 2022 to 2025 while the median one tested aged 3 years. Ageing alone would predict about 7.7 points, so it is holding up better than the fleet average for its age.
| Year | Tests | Median age | Fail rate | All cars | |
|---|---|---|---|---|---|
| 2022 | 17,502 | 7 | 13% | 22.5% | |
| 2023 | 17,413 | 8 | 15.1% | 22.8% | |
| 2024 | 14,769 | 9 | 17.7% | 23.2% | |
| 2025 | 15,926 | 10 | 19.1% | 22.6% |
Fail rate is first attempts at class 4 tests. Median age is the age of a typical Mii at its test that year, and it is the number to watch: across the whole fleet each extra year of age adds roughly 1.9 points to the fail rate, so a model whose age and fail rate rise together is simply getting older.
The exact defects that fail it
Every failure item DVSA recorded against a Mii in 2025, counted by how many tests each one appeared on.
- 1Service brake performance: excessively binding318 tests
- 2Pins and bushes: pin or bush excessively worn291 tests
- 3Tread depth: tread depth below requirements of 1.6mm255 tests
- 4Catalyst emissions: Lambda reading after 2nd fast idle outside specified limits233 tests
- 5Fuel cap/sealing device: ineffective208 tests
- 6Coil spring: fractured or broken208 tests
- 7SRS malfunction indicator lamp: warning lamp indicates a fault194 tests
- 8Position lamp: not working179 tests
What wears out first
Advisories are the tester flagging wear that is still legal. A typical Mii collects 2.29 of them per test, and these are the ones that come up most. Treat it as the running-repairs list for the next year or two.
- 1Condition: has a tear, caused by separation or partial failure of its structure2,233 tests
- 2Tread depth: tread depth below requirements of 1.6mm1,993 tests
- 3Pins and bushes: pin or bush excessively worn1,110 tests
- 4Brake discs: in such a condition that it is seriously weakened1,098 tests
- 5Brake pads: less than 1.5 mm thick628 tests
- 6Service brake performance: excessively binding584 tests
- 7Brake discs: significantly and obviously worn487 tests
- 8Non-component advisories: Play in steering rack inner joint(s)375 tests
Questions
What is the SEAT Mii MOT pass rate?
80.9% of the 15,927 SEAT Mii first-attempt MOTs in 2025 passed. The fail rate of 19.1% compares with 22.6% across all cars. A further 5.9% passed after a defect was fixed during the test visit.
What does a SEAT Mii usually fail on?
The single most common failure is "Service brake performance: excessively binding", recorded on 318 failed tests, followed by "Pins and bushes: pin or bush excessively worn" and "Tread depth: tread depth below requirements of 1.6mm". By section, brakes appears in 31.6% of failures, lamps, reflectors and electrical equipment appears in 25.9% of failures, suspension appears in 25.8% of failures.
Does age change the odds?
Sharply. At 3 to 5 years old the fail rate was 0%; at 10-13 years it was 20.8%. The median SEAT Mii tested in 2025 was 10 years old with 53,343 miles.
Is the SEAT Mii getting less reliable?
The fail rate rose 6.1 points to 19.1% from 2022 to 2025 while the median one tested aged 3 years. Ageing alone would predict about 7.7 points, so it is holding up better than the fleet average for its age.
First-attempt class 4 tests, 2025, from DVSA’s anonymised MOT data (OGL v3, retrieved 2026-09-12). DVSA records newer cars trim by trim; this page adds every Mii trim together. Year-on-year figures come from the same DVSA extracts for 2026 and earlier years. Full method on the pass rates hub.
DVSA has published 4 safety recalls naming the SEAT Mii: SEAT Mii recalls.
Other SEAT models
Checking a particular Mii?
The odds above are the model. The car in front of you has its own record: every test, every advisory, the mileage at each one.
Due a test? Find an approved MOT station near you.