Model Reports
8 min readUpdated 11 Sep 2026
DVSA open data · 8,596 tests analysed
Mercedes-Benz Gla 2020: reliability & common MOT faults
895 first-attempt MOT failures were recorded on the 2020 Mercedes-Benz Gla in 2025. The items recorded most often on them were Tyres — Condition (rear) and Brake pads (front). Figures are among first-attempt failed MOT tests, not among all tests.
Hybrid Glas passed first time 2.6 pp more often than petrol ones (91.9% of 356 vs 89.3% of 7,378).
First-attempt pass
89.6%
of 8,596 first tests (2025)
First tests
8,596
test year 2025
Failed first attempts
895
failed first-attempt tests
Most common fail
14.4%
Tyres — Condition (rear)
MOT pass rates
First-attempt and official-style rates among class 4 first tests of the year.
First-attempt pass
89.6%
of 8,596 first tests (2025)
Official-style pass
91.3%
incl. same-day PRS fixes
First tests
8,596
class 4 · first MOT of the year
Typical age 5.0 yrs · median mileage 33,752 mi
vs 2024:
-1.3 pp first-attempt
Note:
Class 4 cars · first MOT of the year per vehicle · P/PRS/F outcomes (2025 data).
PRS (fixed at the station the same day) counts as a fail in the first-attempt rate.
Raw outcomes for this cohort — not adjusted for age, mileage, or peer mix.
MOT doesn't test engine or gearbox internals.
Common faults
Failure patterns that show up more often on this registration year than on similar cars.
These MOT failure patterns show up more often on this registration year than on
similar cars of the same class, age, and mileage.
Shares below are measured across the 895 failed
first attempts in 2025
that the age-and-mileage comparison can be computed on.
Standout: Drive shafts — Joints (front) — 3.8% of this year's failed first attempts
Recorded on 34 of those tests. It tops the table on elevation — about 3.9× more often than on similar cars of the same age and mileage. That is what makes it unusual for its class, which is a different question from what is most likely to fail; the buying checklist ranks by that. The full ranked list is in the table below.
No patterns met the strongest callout thresholds on this page; showing the highest-lift
rows that still cleared the display floors.
Only patterns that clear minimum sample and elevation thresholds are shown
(at least 20 failures and about
2.0× more often than similar cars).
Note: Rates and comparisons are among first-attempt failed tests, not all MOTs. Patterns come from MOT defect codes — not manufacturer service bulletins, recalls, or a diagnosis of any individual car. Failures and advisories are listed separately.
If you are buying one
What this year's MOT record means for the decision in front of you.
On this year, prefer the hybrid. The petrol cars passed first time 2.6 pp less often, on 7,378 tests.
This year also sits 1.1 pp above the midpoint of the 2019 and 2021 cars either side of it — a real break in the model's own run, not the usual year-on-year drift.
Other Gla years worth knowing about
Newer cars always pass more often, so a plain "best year" list would just
rank by age. These are the years that beat or miss the trend their own
neighbouring years set — the only age-adjusted signal this data supports.
The items that failed 2020 Glas most
often, as a share of the year's failed first attempts. This is what goes
wrong, not what is unusual — the table further up the page covers that.
Tyres — Condition (rear) — recorded on 14.4% of failed first attempts
Brake pads (front) — recorded on 12.3% of failed first attempts
Tread depth (front) — recorded on 11.8% of failed first attempts
Visibility — Washers — recorded on 5.7% of failed first attempts
Every figure here is a first-attempt MOT rate from DVSA open data for this
model line. MOTs do not test engine or gearbox internals, so this is a
pre-purchase checklist, not a full reliability score.
FAQs
Short answers about how to read this model-year guide.
Hybrid Glas passed first time 2.6 pp more often than petrol ones (91.9% of 356 vs 89.3% of 7,378). In 2025, 89.6% of 8,596 first MOTs on the 2020 Mercedes-Benz Gla passed first time (PRS — items fixed at the station the same day — counted as a fail). The official-style rate including PRS is 91.3%. Among 895 failed first-attempt MOT tests (test year 2025), Drive shafts — Joints (front) appears more often than on simi…
Ranked by how often they were actually recorded, the items that failed 2020 Mercedes-Benz Glas most often at the first attempt were Tyres — Condition (rear) (14.4%), Brake pads (front) (12.3%) and Tread depth (front) (11.8%) — each as a share of the year's failed first attempts. That is what goes wrong on the car. It is a different question from which patterns are unusual for the class, which the common-faults table…
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Drive shafts — Joints (front) (3.8% of those tests; 34 observed failures; about 3.9× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Drive shafts — Joints (front) shows up more often than on similar cars (3.8% of those tests; 34 observed failures; about 3.9× more often than similar cars). That does not prove a design fault — age, mileage, and how the car was used still matter. Treat it as a pre-purchase check point, not a manufacturer service bulletin.
Common MOT problem areas for the 2020 Mercedes-Benz Gla include Drive shafts — Joints (front), Coil spring (front). These patterns show up more often than on similar cars after we filter out sparse noise — not a full list of every possible fault on an individual car.
This page highlights MOT failure patterns for the 2020 Mercedes-Benz Gla (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.
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.
20242025
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.
We never invent pass rates, star scores, or ranks when those data marts are missing.