Mercedes Unknown (2009)
2009 Mercedes Unknown
CarHunch analysed 4,536 real MOT records for the 2009 Mercedes Unknown. This breakdown of actual test outcomes — pass rates, defect profiles, mileage data — isn't published anywhere else.
The 2009 Mercedes Unknown has a first-time pass rate of just 2.9%, catastrophically below the UK average of 80%—this cohort is almost entirely failing MOT on first attempt. With a dangerous defect rate of 0.5%, these aren't death-trap vehicles, but the diesel variants (which make up 99% of the data) are performing even worse at 2.3%, suggesting fuel system or emissions issues are endemic to this generation.
At a median mileage of 150,500 miles for a 15-year-old car, these vehicles are being worked hard, and that stress is showing in the pattern: virtually zero failures per vehicle on average (0.03) but concerning systemic issues that aren't registering as hard failures yet. Before buying one, get a full pre-purchase inspection focusing on emissions equipment, fuel injectors, and gearbox health—this isn't a case of random teething troubles, but a model with known structural weaknesses you'll need to budget for.
What to check before buying a 2009 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 (99%) | 4,489 | 2.3% | 0.03 |
| Diesel (1%) | 23 | 88.2% | 0.48 |
| Petrol (0%) | 21 | 32.4% | 0.19 |
| Electric (0%) | 1 | 0% | 0 |
| Diesel (0%) | 1 | 100% | 0 |
| Gas (0%) | 1 | 0% | 0 |
Mileage Distribution
Most 2009 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 2009 Mercedes Unknown vehicles fall between 101,421 and 263,663 miles.
2009 Mercedes Unknown — Still on the Road
Strong survival — 72 vehicles still getting MOTs in 2025, 95% of the peak.
Based on vehicles from this manufacture year that had at least one MOT test in each calendar year. Data from 2016–2025.
MOT History Averages
Most Common MOT Issues — 2009 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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36.9%
Oil leak, but not excessive
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16.4%
Front Brake disc worn, pitted or scored, but not seriously weakened
-
14.8%
Offside Front Brake pipe corroded, covered in grease or other material
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13.1%
Nearside Front Brake pipe corroded, covered in grease or other material
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11.7%
Nearside Rear Inner Tyre worn close to legal limit/worn on edge
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10.7%
Offside Front Tyre worn close to legal limit/worn on edge
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9.4%
Offside Front Brake disc worn, pitted or scored, but not seriously weakened
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9.4%
Parking brake efficiency below requirements
Data covers a 3-year window centred on 2009. 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.