Is the Seat Mii reliable?

On MOT evidence the Seat Mii is above average. It passes 74.3% of tests once age and mileage are accounted for, against a national average of 72.3%. That figure covers 73% of the national age and mileage range, which is enough to quote but not to rank. This measures how often the car meets the MOT standard, not how often it breaks down or what a repair costs.

What is the most common MOT failure on a Seat Mii?

The item recorded most often is "A suspension pin, bush or joint excessively worn", which appears in 11.2% of failed Seat Mii tests. Because one failed test can list several items, these shares do not add up to 100%.

What do testers most often warn about on a Seat Mii?

The most common advisory is "A tyre seriously damaged", noted on 22.4% of all Seat Mii tests. An advisory is not a failure: it flags something that will likely need attention before the next test.

What mileage does a Seat Mii usually have at its MOT?

The average odometer reading recorded at test is 54,365 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.

Which Seat Mii years are the most reliable?

Going by MOT pass rate, Seat Mii cars first registered 2020–2022 do best at 87.3%, and those registered 2011–2013 do worst at 70.3%. But that ordering is mostly age, not build year: almost every model passes less often as it wears, so the newest cars top this list whatever they are. A specific year looking strong here means little on its own; the failure items above, and the individual car's own MOT history, tell you far more.

Does a Seat Mii get harder to pass as it ages?

Yes. At 3 to 5 years old, 87.3% of Seat Mii tests pass. By 12 to 14 years, that falls to 70.3%. Nearly every model follows this pattern, which is why comparing raw pass rates between models is misleading unless age is accounted for.

Are most Seat Mii models petrol or diesel?

Of the Seat Mii cars tested, 93% are petrol, 7% are electric. Fuel type affects which items tend to fail, particularly emissions and exhaust components.

Model reliability file

Seat Mii MOT pass rate & common failures

From 18,638 recorded MOT tests of the Seat Mii, published by DVSA.

Data updated 29 July 2026

Quick answer

The Seat Mii passes 74.3% of MOT tests once results are adjusted for the age and mileage of the cars tested, against a national average of 72.3%. That is above average. Based on 18,638 tests. Its most commonly recorded failure is suspension pin, bush or joint excessively worn, which appears in 11.2% of failed tests. Cars of this model average 54,365 miles on the odometer when tested.

At a glance

Pass rate, adjusted for age and mileage

74.3%national average72.3%unadjusted75.9%range covered73%

The Mii is 2.0 percentage points above the national pass rate once age and mileage are accounted for, which is above average. The unadjusted figure is 75.9%; the difference is what the age and mileage of this model’s fleet was hiding.

DVSA recorded wording

Most common failure items

Share of failed Seat Mii tests in which each item was recorded. One failed test often lists several items, so these do not sum to 100%.

1.A suspension pin, bush or joint excessively worn11.2%
385 occurrencesSuspension arm bush worn explained
2.Tyre tread depth not in accordance with the requirements10.6%
364 occurrencesTyre worn close to the legal limit explained
3.Significant brake effort recorded with no brake applied indicating a binding brake10.4%
357 occurrencesBrake binding or imbalanced across an axle explained
4.A spring or spring component fractured or seriously weakened7.5%
257 occurrencesRoad spring broken or fractured explained
5.A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning7.5%
257 occurrencesLamp not working explained
6.Lambda coefficient outside the default limits or the range specified by the manufacturer7.3%
252 occurrencesEmissions above the permitted limit explained
7.Wiper blade missing or obviously not clearing the windscreen7.3%
250 occurrencesWiper or washer not working properly explained
8.Fuel system leaking, or missing or ineffective filler cap6.7%
230 occurrencesFuel filler cap missing or fuel system leaking explained
9.An SRS malfunction indicator lamp (MIL) indicates a system malfunction6.1%
209 occurrencesAirbag warning lamp on, or airbag missing explained
10.A rear registration plate lamp or light source missing or inoperative in the case of a single lamp or all lamps5.7%
196 occurrencesLamp not working explained

Warnings without a failure

Most common advisories

Share of all Seat Mii tests carrying each advisory. The denominator differs from the failure list above because an advisory can be issued on a car that passed.

1.A tyre seriously damaged22.4%
4,170 testsTyre damaged or deteriorated explained
2.Tyre tread depth not in accordance with the requirements17.6%
3,283 testsTyre worn close to the legal limit explained
3.A suspension pin, bush or joint excessively worn8.9%
1,654 testsSuspension arm bush worn explained
4.Brake disc or drum excessively weakened, insecure or fractured8.2%
1,533 testsBrake disc worn, pitted or scored explained
5.A brake lining or pad worn below 1.5mm4.1%
770 testsBrake drum or shoe worn or contaminated explained
6.Brake disc or drum significantly and obviously worn3.5%
643 testsBrake disc worn, pitted or scored explained
7.Significant brake effort recorded with no brake applied indicating a binding brake3.1%
582 testsBrake binding or imbalanced across an axle explained
8.Brake pipe damaged or excessively corroded2.9%
544 testsBrake pipe corroded explained

The rest of the record

Everything else recorded on the Seat Mii

The 17 other defects testers recorded on this model, beyond the most common listed above. Each links to what it means and what it takes to put right.

Known faults

Seat Mii common problems, by part and by year

The same failure record read the way a buyer asks the question: which parts wear out on a Mii, when they start, and how each registration year compares — including the steps that mark a generation change.

Mii common problems and results by year

How wear changes the picture

Mii pass rate by age and registration year

How often the Seat Mii passes at each age, with the years those cars were first registered. Tests are from 2025, so a car aged 3 to 5 was first used in 2020–2022.

3–5 yrsreg. 2020–202287%

6–8 yrsreg. 2017–201982%

9–11 yrsreg. 2014–201674%

12–14 yrsreg. 2011–201370%

Read this as an age curve rather than a verdict on particular model years. Nearly every car passes less often as it gets older, so a newer Mii outscoring an older one says more about wear than about how that year’s cars were built. Bands holding too few tests to be meaningful are omitted rather than shown as a rate.

What gets tested

The Mii fleet

Average mileage recorded at test: 54,365
Fuel mix of tested cars: Petrol92.7%
Electric7.3%

Check a specific Seat Mii

A model average tells you the pattern. Its own MOT record tells you the car.

Compare within the range

Other Seat models

Seat Ibiza — 66.6% adjusted
Seat Leon — 75.3% adjusted
Seat Arona — 84.2% unadjusted
Seat Ateca — 87.9% unadjusted
Seat Alhambra — 73.2% adjusted
Seat Altea — 59.2% unadjusted
All Seat models

Similar test volumes

Compare against other makes

BMW 7 Series — 85.6% adjusted, ranked 17
Citroen C5 — 69.6% adjusted, ranked 175
Abarth 595 — 76.0% adjusted, ranked 95
Renault Grand Scenic — 59.4% adjusted, ranked 253

Common questions

Is the Seat Mii reliable?: On MOT evidence the Seat Mii is above average. It passes 74.3% of tests once age and mileage are accounted for, against a national average of 72.3%. That figure covers 73% of the national age and mileage range, which is enough to quote but not to rank. This measures how often the car meets the MOT standard, not how often it breaks down or what a repair costs.
What is the most common MOT failure on a Seat Mii?: The item recorded most often is "A suspension pin, bush or joint excessively worn", which appears in 11.2% of failed Seat Mii tests. Because one failed test can list several items, these shares do not add up to 100%.
What do testers most often warn about on a Seat Mii?: The most common advisory is "A tyre seriously damaged", noted on 22.4% of all Seat Mii tests. An advisory is not a failure: it flags something that will likely need attention before the next test.
What mileage does a Seat Mii usually have at its MOT?: The average odometer reading recorded at test is 54,365 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.
Which Seat Mii years are the most reliable?: Going by MOT pass rate, Seat Mii cars first registered 2020–2022 do best at 87.3%, and those registered 2011–2013 do worst at 70.3%. But that ordering is mostly age, not build year: almost every model passes less often as it wears, so the newest cars top this list whatever they are. A specific year looking strong here means little on its own; the failure items above, and the individual car's own MOT history, tell you far more.
Does a Seat Mii get harder to pass as it ages?: Yes. At 3 to 5 years old, 87.3% of Seat Mii tests pass. By 12 to 14 years, that falls to 70.3%. Nearly every model follows this pattern, which is why comparing raw pass rates between models is misleading unless age is accounted for.
Are most Seat Mii models petrol or diesel?: Of the Seat Mii cars tested, 93% are petrol, 7% are electric. Fuel type affects which items tend to fail, particularly emissions and exhaust components.

How this was worked out

Method and limits

Figures come from the DVSA anonymised MOT testing dataset, published under the Open Government Licence. Only class 4 initial tests are counted: retests are excluded so a car appears once, and abandoned tests are excluded entirely. The adjusted rate is directly standardised across twenty-five age and mileage bands and reweighted onto the national distribution, so this model is compared against cars that have lived a similar life rather than against a younger or lighter-used fleet.

An MOT measures whether a car met a legal standard on the day. It is not a breakdown record, a service history or a running-cost estimate, and a pass rate is a property of a fleet rather than a prediction about one car.