Mercedes-Benz GLS 2018: reliability & common MOT faults

At a glance

How 531 first tests went in 2025.

Passed first time: 85 in every 100
Did not pass first time: 15 in every 10077 failed first-attempt tests
The typical car: 7 yearsabout 60,849 miles
First tests counted: 531

How we count this. Data: UK MOT open data, 2025. Only Class 4 cars on their first MOT of the year are counted. A car that fails and is fixed at the test station still counts as a fail in the first-attempt rate. These are raw results, not adjusted for age, mileage, or peer mix. The MOT does not test engine or gearbox internals.

Advisories

Other things testers noted as worn or close to failing, more often than on similar cars.

An advisory is a note from the tester about something that has not failed yet. It is an early warning, not a fail.

Tyre tread depth (rear)

Noted on 20 first tests2.6 times as often as similar carsWear pattern

Data: UK MOT open data, 2025. Counts cover advisories recorded on failed first tests only, compared with cars of the same age and mileage.

MOT pass rates

How first tests ended, and how the pass rates are counted.

Passed first time: 85in every 100; Passed on the first test.
Fixed at the station: 2in every 100; Failed, then fixed at the test station the same day.
Failed: 13in every 100; Did not pass, and were not fixed at the test station.

First-attempt pass 85.5% of 531 first tests (2025): only cars that passed first time count. Official-style pass 86.8%: cars fixed at the test station also count as a pass. The 2 fixed and the 13 not fixed make the 15 in every 100 that did not pass first time.

Same model, other years

Passed first time in every 100, all tested in 2025.

Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 86 in every 100 passed first time.

Year	Passed first time	First tests
2016	87 in every 100	373
2017	89 in every 100	584
2018 This car	85 in every 100	531
2019	85 in every 100	367
2020	86 in every 100	371

FAQs

Short answers about how to read this model-year guide.

Is the 2018 Mercedes-Benz GLS reliable?

With 531 first tests, there are too few to say whether the 2018 Mercedes-Benz GLS differs from the model years either side. Treat the faults below as a checklist. In 2025, 85.5% of 531 first MOTs on the 2018 Mercedes-Benz GLS passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 86.8%. Among 77 failed first-attempt MOT tests (test year 2025), we highlight MOT failure patterns that show up more often than on cars of a similar age and mileage when the sample is large enough to trust. There is no single reliability score here; this is a pre-purchase checklist built from DVSA open data, not a guarantee for any individual car.

How should I read advisories vs fails?

Advisories flag issues noted at the test and are not a fail rate. We show advisory patterns that appear more often than on similar cars among failed first-attempt tests, separate from common failure rows. Use them as early-warning checks, not as a pass/fail score.

What does this Mercedes-Benz GLS 2018 MOT report cover?

This page highlights MOT failure patterns for the 2018 Mercedes-Benz GLS (registration year) using UK DVSA open data for the selected test year. Patterns are compared with cars of a similar age and mileage. It is a buyer checklist from MOT defect statistics, not a full service history or manufacturer service-bulletin list.

Does this include engine and gearbox problems?

No. MOT tests do not cover engine internals, gearboxes, or many electronic modules. Patterns here come from MOT defect statistics only and should not be read as engine or gearbox reliability scores.

About this data

How this page is built and what it can (and can't) say.

These figures come from UK MOT open data for this model year. We surface common failure patterns against similar cars, not a full reliability score, and not a pass/fail verdict on any individual vehicle.

2024 2025

What we include

UK Class 4 cars only. Normal MOT tests (not retests); first test per vehicle per calendar year; results pass, PRS, or fail.

Same-day repairs

PRS means the car failed items that were fixed at the test station and then passed the same day. We count PRS as a first-attempt fail in headline rates so same-day repairs do not hide problems.

How we compare

We compare this model year with other Class 4 cars of similar age and mileage in the same test year. This model family is left out of the peer group so the car is not measured against itself.

What this does not cover

MOTs do not cover engine internals, gearboxes, or many electronics; this is not a full reliability score.
Common faults come from MOT defect stats, not manufacturer TSBs or recalls.
Age and mileage matching reduces, but does not remove, differences in how cars were used and maintained.
If the data for a car is too thin to say anything useful, we say so rather than guess.

Contains public sector information licensed under the Open Government Licence v3.0.