Mercedes Benz 420 (1989)
1989 Mercedes Benz 420
CarHunch analysed 415 real MOT records for the 1989 Mercedes Benz 420. This breakdown of actual test outcomes — pass rates, defect profiles, mileage data — isn't published anywhere else.
The 1989 Mercedes-Benz 420 falls slightly short of the UK average with a first-time pass rate of 76.3% versus 80%, suggesting a moderately reliable classic that demands attention before its MOT. Nearly one in five of these cars (19.5%) have shown a dangerous defect at some point, which is a meaningful concern for a 35-year-old luxury saloon and worth investigating during a pre-purchase inspection.
At an average mileage of 125,466, these cars have typically been used as cherished classics rather than daily drivers, yet they still rack up an average of 2.32 failures and 10.2 advisories per test—pointing to aging components like suspension, brakes, and trim rather than catastrophic failures. Before committing to one, budget for a pre-MOT service and have a Mercedes specialist inspect the cooling system, fuel lines, and electrical harnesses, as these vintage models often need preventative work to keep passing.
What to check before buying a 1989 Mercedes Benz 420
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 Benz 420
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Pass Rate by Fuel Type
| Fuel type | Vehicles | Pass rate | Avg failures |
|---|---|---|---|
| Petrol (100%) | 413 | 76.3% | 2.33 |
| LPG (0%) | 1 | 100% | 0 |
| Diesel (0%) | 1 | 80% | 3 |
Mileage Distribution
Most 1989 Mercedes Benz 420 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 1989 Mercedes Benz 420 vehicles fall between 90,986 and 155,143 miles.
1989 Mercedes Benz 420 — Still on the Road
117 vehicles still getting MOTs in 2025 — 77% of the peak remain.
Based on vehicles from this manufacture year that had at least one MOT test in each calendar year. Data from 2014–2025.
MOT History Averages
Most Common MOT Issues — 1989 Mercedes Benz 420
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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39.7%
Oil leak
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25.8%
Offside Rear Tyre worn close to the legal limit
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24.4%
Nearside Rear Tyre worn close to the legal limit
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22.7%
Offside Front Tyre worn close to the legal limit
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20.8%
Oil leak, but not excessive
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20.3%
Nearside Front Tyre worn close to the legal limit
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19.5%
Steering system has slight free play detected at steering wheel
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18.9%
Exhaust has a minor leak of exhaust gases
Data covers a 3-year window centred on 1989. Counts include advisories and failures.
Found a specific Mercedes Benz 420?
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