Mercedes Benz
4,623 MOT tests analysed. sits above the UK fleet average — here's where Glss pass, fail, and end up on the retest sheet.
That's 11.8 points above the UK fleet average across our 1,984 tracked models — a confident result.
Pass
89.3%
Pass-after-fix
2.3%
Fail
7.9%
Avg miles
59,986
Pass + Pass-after-fix + Fail = 100%
Some examples of this model are borderline — a small number of diesels were certified Euro 6 before September 2015. Check your registration on the government's ULEZ checker to be certain. Daily charges if driven in the zone: London £12.50 · Birmingham £8.00 · Bristol £9.00 .
Performance by cohort
2 year bands · 4,622 tests
Pass rate is broadly flat across the cohorts — new and old Gls examples track each other at the test bay.
Pass
89.3%
Fail
7.7%
PRS
2.7%
Avg mileage at test
65,288 mi
Pass
89.3%
Fail
8.2%
PRS
1.7%
Avg mileage at test
51,307 mi
Cohort = vehicle's first-registration year band. Same model, different generations of build.
The picture
Across 2,252 MOT tests, the Gls returns 88.5% first-time pass — comfortably ahead of the UK fleet average. The single most-logged Major fail is tyre tread under the limit. A split CV-joint boot and windscreen damage round out the top three. Average tested mileage sits at 51,480, 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
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 →
42–50
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A transmission shaft constant velocity joint boot severely deteriorated
131 occurrences · 2.8% of tests
Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view
107 occurrences · 2.3% of tests
A tyre cords visible or damaged
71 occurrences · 1.5% of tests
A tyre seriously damaged
65 occurrences · 1.4% of tests
Tyre tread depth not in accordance with the requirements
64 occurrences · 1.4% of tests
a brake lining or pad worn below 1.5mm
37 occurrences · 0.8% of tests
Number plate does not conform to the specified requirements
33 occurrences · 0.7% of tests
A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc
32 occurrences · 0.7% of tests
Brake lining or pad worn down to wear indicator
18 occurrences · 0.4% of tests
A tyre seriously damaged
18 occurrences · 0.4% 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
£120–£190
If every one of this Gls'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 →
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Build your own retest budget.
Year-band analysis
First-time MOT pass rate split by registration band. Pass rates barely move across bands here, so the year you buy Mercedes Benz Gls makes little measurable difference to MOT outcomes.
Best band to buy
89.3%
2018–2020 registration
the 2018–2020 band climbs to 89.3% — a 0.0-point improvement. Tests in this band average 51,307 miles — roughly 14K miles fewer on the clock than the older band. Failures here are mostly wear items: constant velocity boot severely deteriorated, damaged but not adversely affecting driver's view — the structural issues that drag down older examples don't appear in the top-10 for this band. The stricter post-2018 MOT test rules meant manufacturers had to tighten up emissions and electrical checks, but this band still shows far fewer major failures on suspension and bodywork than the older fleet.
Band to be cautious about
89.3%
Pre-2018 registration
On the older band (pre-2018), the data shows a 89.3% pass rate against a fleet average of 89.3% on the newer band. The main culprits logged at test: constant velocity boot severely deteriorated, damaged but not adversely affecting driver's view, and tread depth below requirements of 1.6mm. Average mileage on test for this band is 65,288 miles — high-mileage wear items are a recurring theme.
Best band to buy: 2018-2020 (89.3% first-time pass). Worst band to avoid: pre-2018 (89.3% pass). That's a 0.0-point spread across 2,865 older tests and 1,757 newer ones — year of build makes a material difference on this model.
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Recall history
The Gls has 10 official UK vehicle recalls covering defect details, remedies, and affected build dates.
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 Gls 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.
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