Mercedes Unknown (2018)
2018 Mercedes Unknown
CarHunch analysed 108 real MOT records for the 2018 Mercedes Unknown. This breakdown of actual test outcomes — pass rates, defect profiles, mileage data — isn't published anywhere else.
This 2018 Mercedes has a first-time pass rate of 56.5%, well below the UK average of 80%, which is a genuine reliability concern for buyers—nearly half fail their MOT on first attempt. The dangerous defect rate is mercifully low at 1.8%, so safety isn't the primary worry here.
The median mileage of just 16,743 miles suggests these are lightly-used vehicles, yet they're still struggling to pass, pointing to age-related wear or maintenance neglect rather than high-mileage abuse. With an average of 0.31 failures and 0.9 advisories per vehicle, minor issues are common; before buying, get a full pre-purchase inspection and budget for immediate remedial work, as this cohort's track record suggests problems often emerge quickly.
What to check before buying a 2018 Mercedes Unknown
Practical pre-purchase checks for this age and model.
- 📋 Check the full MOT history. Look for recurring advisories — slow-building issues like corrosion or brake wear patterns show up years before they become failures. Enter the reg below for a full AI analysis.
- 🔍 Inspect for corrosion in person. Brake pipes, sills, subframes, and chassis legs. Surface rust is normal at this age; structural rust is a serious problem that's expensive to fix and can fail an MOT.
- 🛞 Check tyres and brakes. The most common advisory items at this age. Budget for replacement if they're near the limit — factor this into your offer price.
- 📄 Run an HPI check. The MOT history won't show outstanding finance, insurance write-offs, or stolen status — an HPI check will.
Before you buy a Mercedes Unknown
MOT history is one piece of the puzzle. These checks can reveal what CarHunch can't.
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Pass Rate by Fuel Type
| Fuel type | Vehicles | Pass rate | Avg failures |
|---|---|---|---|
| Diesel (93%) | 100 | 55.5% | 0.32 |
| Petrol (7%) | 8 | 68.8% | 0.25 |
Mileage Distribution
Most 2018 Mercedes Unknown vehicles sit in the blue band. If the car you're looking at is outside it, it's either unusually low or high mileage for its age.
Half of all 2018 Mercedes Unknown vehicles fall between 12,229 and 41,597 miles.
2018 Mercedes Unknown — Still on the Road
Strong survival — 57 vehicles still getting MOTs in 2025, 93% of the peak.
Based on vehicles from this manufacture year that had at least one MOT test in each calendar year. Data from 2019–2025.
MOT History Averages
Most Common MOT Issues — 2018 Mercedes Unknown
Based on actual MOT test records for this model. Percentage shows how often each item appears across all vehicles in this cohort.
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12.3%
Front Brake disc worn, pitted or scored, but not seriously weakened
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10.9%
Parking brake efficiency below requirements
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10.1%
COVID-19 6 MONTH EXTENSION
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7.2%
Nearside Front Tyre worn close to legal limit/worn on edge
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5.8%
Rear Brake disc worn, pitted or scored, but not seriously weakened
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5.8%
Nearside Rear Anti-roll bar linkage pin or bush worn but not resulting in excessive movement
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5.8%
Nearside Headlamp aim too high
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5.8%
Engine MIL inoperative or indicates a malfunction
Data covers a 3-year window centred on 2018. Counts include advisories and failures.
Found a specific Mercedes Unknown?
Enter the reg to see its individual MOT history, AI Hunches, and how it compares to this cohort.