Performance by cohort

3 year bands · 5,361 tests

Pass rate climbs 13.7 points across the cohorts — newer Unclassified examples clear the test more reliably than the early cars.

Pre-2018 cohort 4,842

Pass

75.4%

Fail

18.3%

PRS

4.8%

Avg mileage at test

118,201 mi

2018–2020 cohort 337

Pass

87.8%

Fail

8.0%

PRS

2.7%

Avg mileage at test

24,932 mi

2021+ cohort 182

Pass

89.0%

Fail

6.6%

PRS

3.3%

Avg mileage at test

15,958 mi

Cohort = vehicle's first-registration year band. Same model, different generations of build.

The picture

Unclassified: middle-of-the-pack on first-time pass

Across 2,737 MOT tests, the Unclassified returns 75.8% first-time pass — roughly in line with the UK fleet average. The single most-logged Major fail is windscreen damage. A number-plate lamp out and wipers that don't clear the screen round out the top three. Average tested mileage sits at 110,530, which is the lens to read those failure rankings through. If you own one and the next test is close, the ranked list below is a sensible pre-test checklist.

Top ten reasons for rejection.

Filter failures:

Hide wear items to see the model's real defects.

01

A rear registration plate lamp or light source missing or inoperative in the case of multiple lamps or light sources

128 occurrences · 2.4% of tests
02

Parking brake efficiency below minimum requirement

99 occurrences · 1.8% of tests
03

Brake pipe damaged or excessively corroded

95 occurrences · 1.8% of tests
04

Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view

93 occurrences · 1.7% of tests
05

A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning

84 occurrences · 1.6% of tests
06

A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning

66 occurrences · 1.2% of tests
07

Steering rack gaiter or ball joint dust cover damaged or deteriorated

64 occurrences · 1.2% of tests
08

The aim of a headlamp is not within limits laid down in the requirements

58 occurrences · 1.1% of tests
09

Wiper blade missing or obviously not clearing the windscreen

58 occurrences · 1.1% of tests
10

Service brake efficiency below minimum requirement

50 occurrences · 0.9% of tests

Counts cover Major and Dangerous defects logged at test. Advisory items excluded so this shows why a car was rejected, not just what the tester flagged in passing.

Worst-case fix budget · top 2 failures

£48–£125

If every one of this Unclassified's most-logged Major fails hit at the same MOT, that's the real-world UK garage range. Reality is usually one or two items, not all of them. Open the estimator →

Try the calculator

Build your own retest budget.

Year-band analysis

Best year to buy. Worst to avoid.

First-time MOT pass rate split by registration band. A 13.7-point gap between bands means the year you buy Mercedes Benz Unclassified has a real effect on what turns up at the garage.

Best band to buy

89.0%

2021+ registration

the 2021-on band climbs to 89.0% — a 13.7-point improvement. Tests in this band average 15,958 miles — roughly 102K miles fewer on the clock than the older band. Failures here are mostly wear items: damaged but not adversely affecting driver's view, blade defective — the structural issues that drag down older examples don't appear in the top-10 for this band. Post-2020 examples are early in their MOT life and generally show the cleanest records.

Band to be cautious about

75.4%

Pre-2018 registration

On the older band (pre-2018), the data shows a 75.4% pass rate against a fleet average of 89.0% on the newer band. The main culprits logged at test: inoperative in the case of multiple lamps…, efficiency below requirements, and excessively corroded. Average mileage on test for this band is 118,201 miles — high-mileage wear items are a recurring theme.

Best band to buy: 2021+ (89.0% first-time pass). Worst band to avoid: pre-2018 (75.4% pass). That's a 13.7-point spread across 4,842 older tests and 182 newer ones — year of build makes a material difference on this model.

Year-spread leaderboard →

Tools that pre-empt a retest.

Picked against this car's top failure patterns. Affiliate links to Amazon UK — we earn a small cut at no cost to you. Disclosed up-front, doesn't shape the data.

Item 01 · Amazon UK

H7 / W21W bulb pack

A spare-bulb kit lives in the boot. Test morning is not the time to find your stop-lamp's gone.

Search Amazon UK

My Motor World · affiliate

Parts & supplies for this fix

Affiliate links — small commission, no extra cost to you.

Denso

Denso W14E Spark Plug (Single)

£1.09

View at My Motor World →

Denso

Denso W16EX-U Spark Plug (Single)

£1.09

View at My Motor World →

Denso

Denso W16FSR Spark Plug (Single)

£1.09

View at My Motor World →

Denso

Denso W9LM-US Spark Plug (Single)

£1.09

View at My Motor World →

Click Mechanic · affiliate

Book a mobile mechanic

Affiliate links — small commission, no extra cost to you.

Mobile mechanic · UK-wide

Book a mechanic at your door.

Fixed-price quotes upfront. No garage needed. Click Mechanic sends a vetted local mechanic to you — home, work, or roadside.

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Buying or keeping an Unclassified?

Use the failure ranking as a pre-test checklist or a haggling lever. Treat the headline pass rate as a fleet-wide trend, not a guarantee on any individual car.

If you own an Unclassified and your last MOT looked nothing like the ranked failures above, that's normal — individual cars vary widely. The ranking shows the patterns testers flag most often across the country.