Mercedes Benz
1,711 MOT tests analysed. sits above the UK fleet average — here's where C 300 Amg Line ED Prem D As pass, fail, and end up on the retest sheet.
That's 12.9 points above the UK fleet average across our 1,984 tracked models — a confident result.
Pass
90.4%
Pass-after-fix
1.1%
Fail
8.4%
Avg miles
38,581
Pass + Pass-after-fix + Fail = 100%
Diesel cars registered from September 2015 generally meet Euro 6 — compliant in London ULEZ, Birmingham CAZ, Bristol CAZ, and Glasgow LEZ.
Performance by cohort
2 year bands · 1,711 tests
Pass rate climbs 1.8 points across the cohorts — newer C 300 Amg Line ED Prem D A examples clear the test more reliably than the early cars.
Pass
90.1%
Fail
8.4%
PRS
1.2%
Avg mileage at test
40,095 mi
Pass
91.9%
Fail
8.1%
PRS
0.0%
Avg mileage at test
29,690 mi
Cohort = vehicle's first-registration year band. Same model, different generations of build.
The picture
Across 752 MOT tests, the C 300 Amg Line Ed Prem D A returns 88.4% first-time pass — comfortably ahead of the UK fleet average. The single most-logged Major fail is tyre tread under the limit. A tyre with the cords showing and windscreen damage round out the top three. Average tested mileage sits at 30,180, which is the lens to read those failure rankings through. If you own one and the next test is close, the ranked list below is a sensible pre-test checklist.
ABI Insurance Group
A high-group car — insurance costs will be significantly above average. Lower groups cost less to insure; UK fleet average is around Group 22.
Source: ABI Group Rating Panel · administered by Thatcham Research · groups cover standard variants; performance trims may sit higher. Browse all insurance groups →
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Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view
41 occurrences · 2.4% of tests
Tyre tread depth not in accordance with the requirements
37 occurrences · 2.2% of tests
A tyre cords visible or damaged
29 occurrences · 1.7% of tests
A tyre seriously damaged
25 occurrences · 1.5% of tests
Wiper blade defective
18 occurrences · 1.1% of tests
Excessive fluctuation in brake effort through each wheel revolution.
10 occurrences · 0.6% of tests
Abnormal lag in brake operation on a wheel
8 occurrences · 0.5% of tests
Engine MIL illuminated indicating a malfunction
7 occurrences · 0.4% of tests
a brake lining or pad worn below 1.5mm
7 occurrences · 0.4% of tests
A tyre seriously damaged
6 occurrences · 0.4% of tests
Counts cover Major and Dangerous defects logged at test. Advisory items excluded so this shows why a car was rejected, not just what the tester flagged in passing.
Worst-case fix budget · top 3 failures
£140–£235
If every one of this C 300 Amg Line ED Prem D A's most-logged Major fails hit at the same MOT, that's the real-world UK garage range. Reality is usually one or two items, not all of them. Open the estimator →
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Build your own retest budget.
Year-band analysis
First-time MOT pass rate split by registration band. A 1.9-point gap between bands is modest — the year you buy Mercedes Benz C 300 Amg Line ED Prem D A makes a small but real difference to MOT outcomes.
Best band to buy
91.9%
2021+ registration
the 2021-on band climbs to 91.9% — a 1.9-point improvement. Tests in this band average 29,690 miles — roughly 10K miles fewer on the clock than the older band. Failures here are mostly wear items: has a cut in excess of the…, tread depth below requirements of 1.6mm — the structural issues that drag down older examples don't appear in the top-10 for this band. Post-2020 examples are early in their MOT life and generally show the cleanest records.
Band to be cautious about
90.1%
2018–2020 registration
On the 2018–2020 band, the data shows a 90.1% pass rate against a fleet average of 91.9% on the newer band. The main culprits logged at test: damaged but not adversely affecting driver's view, tread depth below requirements of 1.6mm, and has ply or cords exposed. Average mileage on test for this band is 40,095 miles — high-mileage wear items are a recurring theme.
Best band to buy: 2021+ (91.9% first-time pass). Worst band to avoid: 2018-2020 (90.1% pass). That's a 1.9-point spread across 1,463 older tests and 248 newer ones — year of build makes a material difference on this model.
Picked against this car's top failure patterns. Affiliate links to Amazon UK — we earn a small cut at no cost to you. Disclosed up-front, doesn't shape the data.
Item 01 · Amazon UK
Digital tyre-tread depth gauge
Five quid for a gauge beats £150 for a retest. UK MOT minimum is 1.6mm — most testers fail anything below 2mm to be safe.
Search Amazon UK
Item 02 · Amazon UK
Bosch Aerotwin wiper blades
Cheap wipers fail the test on smear streaks. Bosch Aerotwins last a winter and clear a screen properly.
Search Amazon UK
My Motor World · affiliate
Affiliate links — small commission, no extra cost to you.
Click Mechanic · affiliate
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Mobile mechanic · UK-wide
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Owner reports · Honest John
Verbatim faults logged by owners on honestjohn.co.uk over recent years. We didn't summarise — these are the words people typed in.
What's good
Much improved interior quality. More refined and better to drive than predecessor. Strong 2.0-litre four-cylinder diesel engines on facelifted cars.
Where it falls short
C220 CDI with automatic gearbox is disappointing. Surprising quality issues with pre-facelift models.
Report of electric steering motor failure on 2016 C-Class. Dealer recommends replacing the full steering rack as the motor is part of the component. £2200 for reconditioned unit fitted. Mercedes-Benz UK has offered to cover 50 per cent of the repair cost.
Owner of 220 diesel reports a 9mpg drop in fuel economy after voluntary dealer emissions update.
Further report of front wheels of April 2019 Mercedes Benz C43 AMG "skipping badly when manoeuvring at very low speed resulting in a disconcertingly loud noise akin to having collided with a kerb."
Report of failure of the brakes of 2105 Mercedes Benz C300 D BlueTec hybrid at 88,000 miles. The servo assistance vacuum pump had failed. Needed attention by MB dealer because MB independent not qualified to work on a hybrid. Marshall Care Plan B warranty taken out when car was bought not pay out as it's not a listed part.
Report of rattle from engine of Mercedes-Benz C200 EQ Boost (48v mild hybrid) purchased in May 2019. Within a couple of weeks owner reported a "serious engine rattle" to the supplying Mercedes dealer who said there was nothing wrong with. He then got management involved and they changed a pulley, belt and tensioner, but it made no difference. They then got their group technician involved. He submitted his findings to Mercedes-Benz and they fitted a redesigned crank pulley, but again the noise did not improve so owner served a rejection letter on the dealership and they submitted an exchange vehicle application, but Mercedes said there’s nothing wrong with the car as they have been able to reproduce the noise in some of the other C200 EQ Boosts and they can do some things to reduce the noise.
Report of transmission failure of 2005/65 Mercedes Benz W205 C220 automatic at 35,000 miles; car correctly serviced on time by the MB dealer. Part to repair quoted at £1200 + labour (total of £1,644). MB is not initially offering any help towards cost from a goodwill view point. Car is 8 months out of manufacturer warranty, but owner may have Sale of Goods case law rights.
Report that after the NOx emissions software update a Mercedes-Benz C250d 4matic will not shift up from 8th to 9th gear until 75mph (previously 68mph). 9th can be selected on the paddles, but box shifts back down to 8th at about 65mph.
Report of front wheels of Mercedes-Benz C43 4-Matic 'skipping'.
Report of smell of petrol outside February 2015 Mercedes Benz C200 Sport auto. Will be a blocked charcoal filter in the fuel tank breather system.
Petrol smell reported from March 2016 Mercedes Benz W205 C200 only just out of warranty. Car had its last service with Mercedes in the middle of March. Owner reported to dealer in April 2019 and dealer had the cheek to inform him there would be a £165 'diagnosis fee' to establish the cause of what is actually a very well known problem of the carbon filter in the fuel tank breathing system becoming blocked. Shoud be fixed FoC. Same thing happens on A-Class.
Complaint of 2017 Mercedes-Benz C43 AMG 4-Matic clunking its front tyres on full lock. 4,000 miles from new. Been back to the local Mercedes dealer for investigation under warranty but returned in same the same condition. There are two cures. One is different tyres. But the correct cure is a replacement steering knuckle joint that is correctly engineered for RHD cars.
High speed vibration reported from C350e, particularly noticeable on smooth motorways. Owner has chenged tyres and has a 4-way laser alignment to no avail. MB dealer puzzled. No problem with Airmatic suspension. Seems to be driveline.
Source: honestjohn.co.uk · 30 reports indexed, top 12 shown
Use the failure ranking as a pre-test checklist or a haggling lever. Treat the headline pass rate as a fleet-wide trend, not a guarantee on any individual car.
If you own a C 300 Amg Line ED Prem D A and your last MOT looked nothing like the ranked failures above, that's normal — individual cars vary widely. The ranking shows the patterns testers flag most often across the country.
