Model Reports 8 min read Updated 12 Jul 2026

Mercedes-Benz Cla 2018: reliability & common MOT faults

Elevated MOT failure patterns for the 2018 Mercedes-Benz Cla include Road Wheels — Condition (front) (~12.8× peers) and Individual direction indicators (rear) (~4.6× peers). Based on UK DVSA open data for test year 2025 (1,614 failed first-attempt tests), compared with similar age and mileage peers. Available test years: 2024, 2025.

1,614 failed first-attempt tests · 7,956 first tests (test year 2025)

Standout pattern: Road Wheels — Condition (front) — about 12.8× more often than on similar peer cars.

Key takeaways before you buy

  • Road Wheels — Condition (front): about 12.8× more often than similar cars
  • Individual direction indicators (rear): about 4.6× more often than similar cars
  • Linkage ball joint dust cover (front): about 3.4× more often than similar cars

Common faults

These are MOT failure patterns that show up more often on this registration year than on similar cars of the same class, age band, and mileage in the same test year (leave-one-out peer comparison; whole model family excluded).

Statistical patterns from MOT defect codes — not manufacturer TSBs, recalls, or a diagnosis of any individual car. Fail and advisory patterns are kept separate.

Based on 1,614 failed first-attempt tests in test year 2025.

Road Wheels — Condition (front)

This failure pattern appears about 12.8× more often than on similar peer cars — recorded on 59 failed first-attempt tests; 3.7% of failed tests for this model year.

Front · 59 failures · ×12.8 vs similar cars · 3.7% of failed first tests · Likely common fault pattern

Individual direction indicators (rear)

This failure pattern appears about 4.6× more often than on similar peer cars — recorded on 37 failed first-attempt tests; 2.3% of failed tests for this model year.

Rear · 37 failures · ×4.6 vs similar cars · 2.3% of failed first tests · Likely common fault pattern

No patterns met the strongest callout thresholds on this page; showing the highest-lift rows that still cleared the display floors.

# Fault pattern Location Failures vs similar cars Share of fails Confidence
1 Road Wheels — Condition (front)
Road Wheels > Condition
 Front 59 ×12.8 3.7% Likely common fault pattern
2 Individual direction indicators (rear)
Lamps, reflectors and electrical equipment > Direction indicators > Flashing type > Individual direction indicators
 Rear 37 ×4.6 2.3% Likely common fault pattern
3 Linkage ball joint dust cover (front)
Suspension > Anti-roll bars > Linkage ball joint dust cover
 Front 37 ×3.4 2.3% Likely common fault pattern
4 Malfunction indicator lamp
Noise, emissions and leaks > Exhaust emissions > Spark ignition > Malfunction indicator lamp
 Any 103 ×2.1 6.4% Possible elevated fault

Only patterns that clear minimum sample and elevation thresholds are shown (at least 20 failures and 2.0× peer lift).

Wear patterns

These patterns look like wear or usage effects rather than model-specific design faults. Tyres, brake friction material, and alignment-related defects often track mileage and road use. They are not treated as a model design fault in our common-faults ranking.

# Pattern Location Failures vs similar cars Share of fails Confidence
1 Tyres — Condition (front)
Tyres > Condition
 Front 335 ×2.1 20.8% Wear / usage pattern — not treated as a model design fault

Advisories

Advisory items recorded on failed first-attempt tests that appear elevated versus peers. Advisories are not a fail rate — they flag issues noted at the test, often before they become failures.

# Advisory pattern Location Notes vs similar cars Share Confidence
1 Individual direction indicators (rear)
Lamps, reflectors and electrical equipment > Direction indicators > Flashing type > Individual direction indicators
 Rear 33 ×5.5 2.0% Likely common fault pattern
2 Road Wheels — Condition (front)
Road Wheels > Condition
 Front 30 ×2.2 1.9% Likely common fault pattern

FAQs

We do not show a single reliability score for the 2018 Mercedes-Benz Cla on this page. Among 1,614 failed first-attempt MOT tests (test year 2025), Road Wheels — Condition (front) appears more often than on similar peer cars (about 12.8× more often than peers; 59 observed failures; 3.7% of failed tests). Treat this as a pre-purchase checklist from DVSA open data — not a guarantee for any individual car.
Among failed first-attempt tests we surface patterns that appear more often than on similar peer cars. Top example: Road Wheels — Condition (front) (about 12.8× more often than peers; 59 observed failures; 3.7% of failed tests). These are statistical signals, not a diagnosis of any individual car.
Road Wheels — Condition (front) shows up more often than on similar peer cars (about 12.8× more often than peers; 59 observed failures; 3.7% of failed tests). That does not prove a causal design fault — age, mileage, and usage still matter. Treat it as a pre-purchase check point, not a manufacturer TSB.
Common MOT problem areas for the 2018 Mercedes-Benz Cla include Road Wheels — Condition (front), Individual direction indicators (rear), Linkage ball joint dust cover (front). These are elevated versus similar peer cars where lift clears our floors — not a full list of every possible fault on an individual car.
Advisories flag issues noted at the test and are not a fail rate. We show advisory patterns that look elevated versus peers 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 elevated MOT failure patterns for the 2018 Mercedes-Benz Cla (registration year) using UK DVSA open data for the selected test year. Patterns are ranked against similar age and mileage peers. It is a buyer checklist from MOT defect statistics — not a full service history or manufacturer TSB 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.
PRS means the vehicle 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.

About this data

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

PRS policy. PRS means the vehicle 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.

Peer baseline. We compare this model year with other class 4 cars of similar age and mileage in the same test year, excluding the whole model family so the car is not compared with itself (leave-one-out peer baseline).

Data years. Test years covered: 2024, 2025.

Limitations.

  • MOT tests do not cover engine internals, gearboxes, or many electronic modules — so this is not a full reliability score.
  • Common faults are inferred from MOT defect statistics, not manufacturer TSBs or recalls.
  • Matching on age and mileage reduces but does not remove every usage or maintenance difference between cars.
  • Pass rates and star scores appear only when those data marts are available; this page never invents them.

Display rules config: 1

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

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