Model Reports 4 min read Updated 18 Oct 2026

MG 3 2018: reliability & common MOT faults

In 2025, 72 in every 100 first MOTs on a 2018 MG 3 were passes. Most common reason for a fail: Tyre condition (front).

Summary

The 2018 MG 3 follows the pattern of the model years either side.

At a glance

How 2,441 first tests went in 2025.

Passed first time
72 in every 100
Did not pass first time
28 in every 100692 failed first-attempt tests
The typical car
7 yearsabout 38,894 miles
First tests counted
2,441

What failed most often

  1. Tyre condition (front)12 in every 100 failed tests
  2. Handbrake efficiency below minimum (roller test)12 in every 100 failed tests
  3. Coil spring (rear)12 in every 100 failed tests

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.

Note:

These are patterns across 2018 MG 3 vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. A wear pattern follows age and use more than the way the car was built. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.

Brakes

One fault and one wear pattern. The strongest is the handbrake efficiency below minimum (roller test): 8.2 times as often as on similar cars.

Figures below are measured across the 692 failed first attempts in 2025 that had a mileage recorded, which allows a like-for-like comparison.

We only list faults with at least 20 failures and a rate of about 2.0 times that of similar cars, which keeps one-off results out of the list.

Handbrake efficiency below minimum (roller test)

Failed on 85 first tests8.2 times as often as similar carsLikely evidence

What it means

A parking brake with efficiency below the minimum requirement is Major, and graded Dangerous where efficiency is less than half of the required value. On a roller brake tester, the requirement counts as met if more than half of the wheels of a brake system lock. The check applies only to vehicles whose parking brake was not already tested as the secondary brake.

Brake discs (front)

Failed on 30 first tests2.3 times as often as similar carsWear pattern

What it means

A brake disc or drum must be significantly worn before it is rejected, and being worn below the manufacturer's recommended limits is not a reason in itself. Significantly and obviously worn is Major, as is contamination with oil or grease. A disc or drum that is fractured, insecure, seriously weakened or missing is graded Dangerous.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Seat belts and restraints

One fault: airbag warning light, 6.0 times as often as on similar cars.

Airbag warning light

Failed on 40 first tests6.0 times as often as similar carsLikely evidence

What it means

The airbag warning lamp (SRS MIL in DVSA's wording) is failed only if it indicates a system malfunction, which is Major. A lamp lit to show the passenger airbag is disabled is not to be regarded as a defect. Dashboard messages are not a defect in their own right, though they can help the tester confirm a malfunction.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Suspension

One fault: coil spring (rear), 4.0 times as often as on similar cars.

Coil spring (rear)

Failed on 83 first tests4.0 times as often as similar carsLikely evidence

What it means

A missing bump stop rubber is not a reason to fail a coil spring. When the vehicle is jacked and lowered, a spring that does not correctly locate as the suspension returns to its normal running position is rejected as insecurely attached. A missing spring is Major, and graded Dangerous where directional control is affected.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 34 first tests, 10 times as often as on similar cars.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.

Lamps and electrical

One fault: brake light (rear), 2.3 times as often as on similar cars.

Brake light (rear)

Failed on 25 first tests2.3 times as often as similar carsPossible evidence

What it means

All stop lamps missing or not working is graded Dangerous, and so is a stop lamp that stays on when the brakes are released. A stop lamp that is missing or not working is Major. On some vehicles with LED rear lamps, part of the stop lamp can go out when the rear fog lamp is lit, which is not regarded as a defect.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Tyres

One wear pattern: tyre pressure monitoring system, 2.1 times as often as on similar cars.

Tyre pressure monitoring system

Failed on 36 first tests2.1 times as often as similar carsWear pattern

What it means

A tyre pressure monitoring system that is obviously inoperative is graded Major, and so is one listed as malfunctioning or obviously inoperative. The Minor row uses the word malfunctioning too, but its detail is a warning lamp indicating a fault, and it also covers a tyre that is obviously under-inflated.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

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. Advisories for the faults above are shown with those faults.

Suspension arm (front)

Noted on 59 first tests72 times as often as similar carsElevated evidence

Suspension sub-frame (front)

Noted on 60 first tests47 times as often as similar carsElevated evidence

Rigid brake pipes (front)

Noted on 33 first tests8.3 times as often as similar carsElevated evidence

Non-component advisories

Noted on 36 first tests2.4 times as often as similar carsElevated evidence

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
72in every 100
Passed on the first test.
Fixed at the station
6in every 100
Failed, then fixed at the test station the same day.
Failed
22in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 71.7% of 2,441 first tests (2025): only cars that passed first time count. Official-style pass 77.8%: cars fixed at the test station also count as a pass. The 6 fixed and the 22 not fixed make the 28 in every 100 that did not pass first time.

Same model, other years

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

406080100201420152016201720182019202020212022Older carsNewer cars
4060801002018Older carsNewer cars

Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 76 in every 100 passed first time.

YearPassed first timeFirst tests
201467 in every 1001,443
201565 in every 1002,139
201671 in every 1002,888
201769 in every 1002,714
2018 This car72 in every 1002,441
201975 in every 1003,477
202079 in every 1002,366
202182 in every 1001,868
202285 in every 1003,999

If you are buying one

What this year's MOT record means for the decision in front of you.

Mileage matters most on a 2018 MG 3.

Of 2018 MG 3 vehicles with under 25,000 miles, 84 in every 100 passed their 2025 MOT first time. With 57,000 miles or more, 56 in every 100 did.

Under 25,000491 tests
84
25,000–34,000464 tests
76
34,000–44,000 Typical car535 tests
73
44,000–57,000472 tests
69
57,000 and over478 tests
56

What to check at your mileage

How often each fault turned up on a failed first test, by the car's mileage. Read it as: what is likely to need looking at on a car like the one in front of you.

Under 25,00034,000–44,00057,000 and over
Tyre condition (front)4.12.84.0
Handbrake efficiency below minimum (roller test)0.43.010.0
Coil spring (rear)1.23.28.6
Windscreen wipers (front)2.21.72.3

Faults per 100 first tests, by the car's mileage at the test.

When a car fails

45in every 100

of failed cars had one item to fix.

28in every 100

of failed cars had three or more items to fix.

7in every 100

of all first tests had a defect the tester marked dangerous (unsafe to drive away).

Every figure here is a first-attempt MOT rate from DVSA open data for this model line, for cars of this model year tested in 2025. Each mileage band holds a fifth of the tests. 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.

The 2018 MG 3 follows the pattern of the model years either side. Its main cause of failure was Tyre condition (front), about 12 in every 100 failed tests. In 2025, 71.7% of 2,441 first MOTs on the 2018 MG 3 passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 77.8%. Among 692 failed first-attempt MOT tests (test year 2025), Handbrake efficiency below minimum (roller test) appears more often than on similar cars (12.3% of those tests; 85 observed failures; about 8.2× more often than similar cars). 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.
Ranked by how often they were actually recorded, the items that most often failed a 2018 MG 3 at the first attempt were Tyre condition (front) (12.3%), Handbrake efficiency below minimum (roller test) (12.3%) and Coil spring (rear) (12.0%), each as a share of the year's failed first attempts. That is what goes wrong most often on the car. The common faults table shows a different measure: faults that are unusual compared with similar cars.
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Handbrake efficiency below minimum (roller test) (12.3% of those tests; 85 observed failures; about 8.2× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Handbrake efficiency below minimum (roller test) shows up more often than on similar cars (12.3% of those tests; 85 observed failures; about 8.2× 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 checkpoint, not a manufacturer service bulletin.
Common MOT problem areas for the 2018 MG 3 include Handbrake efficiency below minimum (roller test), Airbag warning light, Coil spring (rear). These are the faults that stand out compared with similar cars, not a complete list of what can go wrong on any individual car.
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.
This page highlights MOT failure patterns for the 2018 MG 3 (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.

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.

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