Performance by cohort

3 year bands · 4,685 tests

Pass rate climbs 5.1 points across the cohorts — newer G examples clear the test more reliably than the early cars.

Pre-2018 cohort 152

Pass

90.8%

Fail

8.6%

PRS

0.0%

Avg mileage at test

42,392 mi

2018–2020 cohort 3,256

Pass

94.0%

Fail

4.4%

PRS

0.6%

Avg mileage at test

36,087 mi

2021+ cohort 1,277

Pass

95.8%

Fail

3.8%

PRS

0.3%

Avg mileage at test

23,552 mi

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

The picture

G: a strong MOT record by UK norms

Across 1,014 MOT tests, the G returns 91.4% first-time pass — comfortably ahead of the UK fleet average. The single most-logged Major fail is a non-conforming number plate. Windscreen damage and a seriously damaged tyre round out the top three. Average tested mileage sits at 29,092, 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.

ABI Insurance Group

Group 28–46

A high-group car — insurance costs will be significantly above average. Lower groups cost less to insure; UK fleet average is around Group 22.

Source: ABI Group Rating Panel · administered by Thatcham Research · groups cover standard variants; performance trims may sit higher. Browse all insurance groups →

28–46

out of 50

Compare quotes →

Top ten reasons for rejection.

Filter failures:

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

01

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

61 occurrences · 1.3% of tests
02

Number plate does not conform to the specified requirements

40 occurrences · 0.9% of tests
03

A tyre seriously damaged

37 occurrences · 0.8% of tests
04

Windscreen or window excessively tinted but not adversely affecting driver's view

30 occurrences · 0.6% of tests
05

Tyre tread depth not in accordance with the requirements

29 occurrences · 0.6% of tests
06

Wiper blade defective

24 occurrences · 0.5% of tests
07

Steering rack gaiter or ball joint dust cover damaged or deteriorated

21 occurrences · 0.4% of tests
08

A tyre seriously damaged

16 occurrences · 0.3% of tests
09

A tyre cords visible or damaged

13 occurrences · 0.3% of tests
10

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

10 occurrences · 0.2% 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

£75–£130

If every one of this G'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 5.1-point gap between bands means the year you buy Mercedes Benz G has a real effect on what turns up at the garage.

Best band to buy

95.8%

2021+ registration

the 2021-on band climbs to 95.8% — a 5.1-point improvement. Tests in this band average 23,552 miles — roughly 19K miles fewer on the clock than the older band. Failures here are mostly wear items: has a cut in excess of the…, tread depth below requirements of 1.6mm — 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

90.8%

Pre-2018 registration

On the older band (pre-2018), the data shows a 90.8% pass rate against a fleet average of 95.8% on the newer band. The main culprits logged at test: ball joint dust cover damaged or deteriorated, but preventing the ingress of dirt, projected beam image is obviously incorrect, and does not conform to the specified requirements. Average mileage on test for this band is 42,392 miles — high-mileage wear items are a recurring theme.

Best band to buy: 2021+ (95.8% first-time pass). Worst band to avoid: pre-2018 (90.8% pass). That's a 5.1-point spread across 152 older tests and 1,277 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

MOT-spec replacement number plate

Faded or non-standard plates fail outright. Replacements take ten minutes online with V5C details.

Search Amazon UK

Item 02 · Amazon UK

Digital tyre-tread depth gauge

Five quid for a gauge beats £150 for a retest. UK MOT minimum is 1.6mm — most testers fail anything below 2mm to be safe.

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 a G?

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 a G 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.