Mercedes C-Class W205 (2014-2021) Reliability Guide
The Mercedes C-Class W205 , produced between 2014 and 2021, marks a real step upmarket compared to the W204. With its design inspired by the S-Class, its modern interior and its numerous technologies, it has appealed to a wide audience.
In terms of reliability, the W205 is generally considered more reliable than the W204 , especially with the newer engines. However, some engines and electronic systems have weaknesses that should be considered before buying a used one.
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Reliability of petrol engines
C180 / C200 / C250 (1.6 and 2.0 turbo – M274 block)
Positive points : modern and efficient engine with good driving pleasure.
Known weaknesses :
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Sensitive timing chain on early models, rattling noise on start-up.
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Coils and pressure sensors (MAP) are sometimes fragile.
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High oil consumption on some models.
How to check before buying :
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Cold start: listen for a clunk or click in the first 1-3 seconds.
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Request maintenance invoices: chain/tensioner replacement or not.
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Check oil level and oil loss after 10,000-15,000 km.
Recommendation : favor models after 2017 or those mentioning significant timing belt maintenance.
C300 (2.0 turbo – M274 then M264)
Positive points : an interesting petrol alternative in terms of power and economy.
Weak points : the same as on the M274 (distribution, fuel consumption) for the older version. The M264 engine introduced after 2018 is more reliable.
How to check before buying :
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Opt for models that were restyled after 2018.
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Check that the service history mentions high-quality oil and regular oil changes.
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Acceleration test and absence of turbo whistling.
Recommendation : excellent compromise, but beware of versions prior to the facelift.
C400 / C43 AMG (V6 3.0 biturbo – M276)
Positive points : high performance, overall solid engine.
Weak points : "AMG" coils, valve wear in direct injection, higher maintenance cost.
How to check before buying :
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Complete maintenance process at AMG or specialist.
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Check oil consumption and for leaks around the turbocharger or manifold.
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Opt for a vehicle that has not been reprogrammed or whose modifications are documented.
Recommendation : high-performance but demanding version.
C63 AMG (V8 4.0 biturbo – M177)
Positive points : legendary engine, very mechanically robust.
Weak points : oil leaks on turbos, oil consumption, expensive maintenance.
How to check before buying :
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Check major service history (turbo, clutch, brake pads, tires).
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Check for absence of blue smoke, oil level too low.
Recommendation : very good engine but high maintenance costs.
Reliability of diesel engines
C200d / C220d / C250d (2.1 L – OM651)
Positive points : already proven engine (W204).
Weak points : fragile injectors, sometimes noisy chain, EGR/DPF valve gets clogged in urban use.
How to check before buying :
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Cold start: no metallic chain noise.
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Check injector or EGR replacement history.
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Test for black smoke during acceleration, and "long journey" maintenance for DPF.
Recommendation : diesel is a good choice, but prioritize mixed/highway use.
C220d / C300d (2.0 L – OM654, from 2018)
Positive points : modern engine, less fouling, better anti-pollution management.
Weak points : cost of AdBlue, electronic complexity.
How to check before buying :
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Check for absence of AdBlue messages and proper system operation.
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Tested cold then hot without jerking, no smoke.
Recommendation : diesel version is the most reliable in the W205 range.
Hybrids (C300h / C350e)
Positive points : interesting technologies, low consumption.
Weak points : high voltage battery, complex electronics, high maintenance cost.
How to check before buying :
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Request battery history and hybridization services.
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Check electrical mode operation, absence of HV fault message.
Recommendation : a good choice if used in urban areas and with a budget for maintenance.
Electronic devices & equipment
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General median: COMAND / MBUX system sometimes capricious.
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Automatic gearbox: 7G-Tronic (phase 1) then 9G-Tronic (from 2018). Both are reliable if the fluid is changed regularly.
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Suspension: AIRMATIC version available as an option, very comfortable but expensive to repair (air cushion, compressor)
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Miscellaneous: panoramic roof (risk of noise or leaks), start-stop battery, ABS/ESP sensors.
How to check before buying : test all equipment (air conditioning, GPS, camera, parking assistance), check for any error indicators, test on several types of roads.
Purchase recommendations
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Prefer the model after 2018 (facelift) .
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Demand a complete service history, invoices, and consistent mileage.
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Check the timing belt, turbocharger, chain, and injectors according to the engine.
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Road test of at least 20-30 km with checks when cold and hot.
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Check the condition of the tires, discs, pads, and silent blocks.
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For primarily urban use, avoid older diesel models or the AIRMATIC version.
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Maintenance budget to anticipate: AMG or hybrid version = higher cost.
Which model should be preferred/avoided?
Preferred option :
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Diesel OM654 (post 2018)
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Petrol C300 M264 (after 2018)
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C43 AMG (good compromise between sportiness and reliability)
To be avoided or monitored with caution :
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Petrol M274 (pre-2017)
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Diesel OM651 (2014-2017)
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Hybrids are suitable for short-term use and uncertain maintenance.
FAQ
Is the Mercedes C-Class W205 reliable?
Yes, overall it is more reliable than the previous generation (W204) but this depends heavily on the engine, maintenance and usage.
Which is the best petrol engine?
The 2.0 turbo M264 (C300 after 2018) appears to be the most reliable in the series.
Which is the best diesel engine?
The 2.0 diesel OM654 (from 2018 onwards) is the preferred choice for its modernity and reliability.
Is the automatic transmission reliable?
Yes, the 7G-Tronic and 9G-Tronic are reliable if oil changes and maintenance are respected.
Conclusion
The Mercedes C-Class W205 remains an excellent used car option, provided you choose the right engine, check the service history, and conduct a thorough test drive. Post-2018 models are preferable, and AMG or hybrid models require a larger maintenance budget.
