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1,910 tests in 2025

Mercedes Unclassified reliability and MOT pass rate

81% passed first time. The 19% fail rate is 3.6 points better than the all-car average, on a median example 18 years old with 69,576 miles.

MOT pass rates / Mercedes

Pass rate

81%

22.6% of all cars failed; 19% of these did.

Fixed on the day

4.5%

Passed after a defect was put right during the visit.

Median at test

69,576 mi

18 years old.

Fail rate by age

Age at testTestsFail rate
3-5 years2815.7%
6-9 years167—
10-13 years24114.9%
14+ years1,21824%

What the Unclassified 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.

  1. Lamps, reflectors and electrical equipment8 dangerous42.3%
  2. Brakes43 dangerous42%
  3. Suspension11 dangerous25.1%
  4. Body, chassis, structure8 dangerous18.2%
  5. Visibility18%
  6. Tyres52 dangerous16%
  7. Steering2 dangerous11.6%
  8. Seat belts and supplementary restraint systems8%

Is the Unclassified getting worse?

The fail rate fell 4.2 points to 19% from 2022 to 2025 while the median one tested aged 1 year. Ageing alone would predict about -0.3 points, so it is holding up better than the fleet average for its age.

YearTestsMedian ageFail rate All cars
20221,8771723.2%22.5%
20231,9121720.9%22.8%
20241,6591820.9%23.2%
20251,9101819%22.6%

Fail rate is first attempts at class 4 tests. Median age is the age of a typical Unclassified 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 Unclassified in 2025, counted by how many tests each one appeared on.

  1. 1Rbt (sp): efficiency below requirements29 tests
  2. 2Rear fog lamp: not working28 tests
  3. 3Position lamp: not working25 tests
  4. 4Wipers: does not clear the windscreen effectively25 tests
  5. 5Service brake performance: efficiency below requirements23 tests
  6. 6Headlamp aim: projected beam image is obviously incorrect20 tests
  7. 7Washers: not working20 tests
  8. 8Rigid brake pipes: excessively corroded20 tests

What wears out first

Advisories are the tester flagging wear that is still legal. A typical Unclassified collects 2.9 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.

  1. 1Brake discs: in such a condition that it is seriously weakened176 tests
  2. 2Rigid brake pipes: excessively corroded169 tests
  3. 3Engine oil leaks: leaking excessively from engine130 tests
  4. 4Tread depth: tread depth below requirements of 1.6mm128 tests
  5. 5Condition: has a tear, caused by separation or partial failure of its structure107 tests
  6. 6Exhaust system: has a major leak of exhaust gases60 tests
  7. 7Pins and bushes: pin or bush excessively worn59 tests
  8. 8Non-component advisories: Play in steering rack inner joint(s)55 tests

Questions

What is the Mercedes Unclassified MOT pass rate?

81% of the 1,910 Mercedes Unclassified first-attempt MOTs in 2025 passed. The fail rate of 19% compares with 22.6% across all cars. A further 4.5% passed after a defect was fixed during the test visit.

What does a Mercedes Unclassified usually fail on?

The single most common failure is "Rbt (sp): efficiency below requirements", recorded on 29 failed tests, followed by "Rear fog lamp: not working" and "Position lamp: not working". By section, lamps, reflectors and electrical equipment appears in 42.3% of failures, brakes appears in 42% of failures, suspension appears in 25.1% of failures.

Does age change the odds?

Sharply. At 3 to 5 years old the fail rate was 5.7%; at 14+ years it was 24%. The median Mercedes Unclassified tested in 2025 was 18 years old with 69,576 miles.

Is the Mercedes Unclassified getting less reliable?

The fail rate fell 4.2 points to 19% from 2022 to 2025 while the median one tested aged 1 year. Ageing alone would predict about -0.3 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 Unclassified trim together. Year-on-year figures come from the same DVSA extracts for 2026 and earlier years. Full method on the pass rates hub.

Checking a particular Unclassified?

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.