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Audi A4 vs Mercedes-Benz C-Class: which is the better used buy?

On DVSA MOT records the Audi A4 and the Mercedes-Benz C-Class are too close to call — 0.3 percentage points apart on first-time MOT passes once you allow for the age of each fleet, which is inside what the choice of cars counted can move. A winner is named only at 2 points or more. A pass with rectification at the station counts as a pass here, and as a failure in DVSA's own initial-test measure. Choose on the fault patterns and running costs below.

MOT first-time pass rate

Counted from DVSA’s anonymised MOT test records. “vs age-matched” compares each model against what the national fleet scores at the same age — the only fair better-or-worse number, because an older fleet fails more whatever its build quality.

Audi A4
Pass rate77.3%
Age-matched national75.0%
Difference+2.3
Tests24,990
Mercedes-Benz C-Class
Pass rate78.6%
Age-matched national76.0%
Difference+2.6
Tests37,418

These figures count every generation still on the road, not only the one described below: mostly Audi A4s registered 2003–2022 and Mercedes-Benz C-Class registered 2002–2022.

Source: DVSA MOT Anonymised Data 2025 (Open Government Licence v3.0). National first-time pass rate 77.3%. Class 4 tests in Great Britain, test type NT (a normal annual test), retests excluded. A pass, or a pass with rectification at the station, counts as a first-time pass; DVSA's own initial-test measure counts a rectified pass as a failure and so reports a lower figure. Testing in Northern Ireland is run separately by the DVA under its own rules. The difference is worked out before rounding, so it can be 0.1 away from the two rounded figures beside it.

Audi A4

B9 (2015–2023) · D-segment executive saloon and Avant estate. One of the most popular used premium cars in the UK alongside the BMW 3 Series. Available as saloon and Avant estate. Key engines: 2.0 TFSI petrol (150–252 PS), 2.0 TDI diesel (136–190 PS), 35 TFSI mild hybrid (150 PS), 40 TFSI (190 PS), 40 TDI (204 PS).

The Audi A4 B9 is a premium, refined executive car with strong build quality, but it requires disciplined Audi specialist maintenance to keep running costs manageable. The 2.0 TDI diesel is reliable on motorway mileage but has documented timing belt (not chain) service requirements — belt failure on the B9 2.0 TDI is an engine-write-off event. The 2.0 TFSI mild hybrid (post-2019) is the better choice for mixed UK driving. Avoid any B9 A4 without full documented service history — Audi's repair costs are high and an unmaintained A4 can quickly become very expensive.

What goes wrong

  • Safety recall R/2020/138recall
    Moisture may enter the belt-driven starter-alternator
    34,982 vehicles in the whole recall (DVSA’s figure for every model it covers) · built between 1 June 2017 and 31 March 2020
    Large recall — 34,982 vehicles. Check a car by registration on GOV.UK.
  • Safety recall R/2020/265recall
    Moisture may enter the belt driven starter-alternator
    11,936 vehicles in the whole recall (DVSA’s figure for every model it covers) · built between 10 August 2018 and 11 March 2020
    Large recall — 11,936 vehicles. Check a car by registration on GOV.UK.
  • 2.0 TDI timing belt service (interference engine)critical
    No audible warning — belt failure is sudden and catastrophic. Prevention through scheduled service is the only protection.
    All B9 A4 2.0 TDI (2015–2023) · Audi recommended interval: every 80,000 miles or 4 years (whichever first). Many specialists recommend 55,000 miles or 4 years in UK stop-start conditions. · £700–£1,200 timing belt kit (preventive); £8,000–£15,000+ engine replacement if belt fails (the 2.0 TDI is an interference engine — belt failure destroys the engine)
    Check: Ask for documented timing belt replacement history. If the car is at 55,000+ miles with no record of a belt change, factor the service into the purchase price or walk away. The 2.0 TDI's timing belt is one of the most important pre-purchase checks on any B9 A4. The 2.0 TFSI petrol uses a timing chain, but the pre-facelift 1.4 TFSI has a toothed belt too, so ask for its belt history as well.
  • MMI infotainment and virtual cockpit freezingminor
    MMI screen freeze; navigation crash; virtual cockpit going blank; MMI reboot loops
    2015–2019 (older MMI generations) · Not mileage-related — software degradation over time · £0 — software update at Audi dealer; hardware replacement £600–£1,200 if MMI control unit fails
    Check: Test all MMI functions during the test drive — navigation, Bluetooth, media, climate control (which is MMI-integrated on many trims). Ask if the latest Audi software update has been applied. Most MMI issues are software-related and resolved by an update.
Typical asking price:
£6,495–£18,995, median £11,495 (middle 80% and median, cars on Autoza on 29 October 2026)
Fuel economy:
49–57 mpg (2.0 TDI real-world UK motorway mixed); 38–47 mpg (35 TFSI MHEV real-world)
Vehicle tax:
£200/year standard rate from the second year, hybrids included — the alternative-fuel discount ended on 1 April 2025. A car registered from April 2017 with a list price over £40,000 when new adds the £440/year Expensive Car Supplement in years 2–6 (£640 in all). Cars registered 2001–2017 pay a CO2 band, roughly £20–£790/year (2026/27 rates).
Best years:
2020, 2021
Years to avoid:
2015
Used Audi A4s for saleFull A4 fault guideUsed Audis

Also compare:

Mercedes-Benz C-Class

W205 (2014–2021) / W206 (2021–present) · D-segment executive saloon, estate (T-Model), and coupe (C205). Direct competitor to BMW 3 Series and Audi A4. Available with petrol (C180, C200, C300), diesel (C200d, C220d, C300d), and PHEV (C300e/de) engines. One of the most popular used premium cars in the UK.

The Mercedes C-Class W205 is a beautifully built executive car. Owners most often report electrical faults, AIRMATIC air-suspension problems and oil leaks, plus timing-chain issues on pre-2016 M274 petrols and oil leaks on early OM651 diesels. A good independent Mercedes specialist keeps running costs manageable. Target the mid-2018 facelift or later.

What goes wrong

  • Safety recall R/2021/134recall
    The behaviour of the emergency call system might not meet specifications
    162,581 vehicles in the whole recall (DVSA’s figure for every model it covers) · built between 4 January 2016 and 29 January 2021
    Large recall — 162,581 vehicles. Check a car by registration on GOV.UK.
  • Safety recall R/2021/110recall
    The behaviour of the emergency call system might not meet specifications
    108,971 vehicles in the whole recall (DVSA’s figure for every model it covers) · built between 4 January 2016 and 29 January 2021
    Large recall — 108,971 vehicles. Check a car by registration on GOV.UK.
  • M274 engine timing chain (C200/C250 petrol, pre-2016)critical
    Rattling on cold start from the rear of the engine; timing-related engine management codes; rough running
    W205 2014–2016 with M274 engine (C180, C200, C250) · From 50,000 miles; higher risk above 60,000 miles · £1,500–£3,500 timing chain replacement; more if engine damage has occurred
    Check: Listen for chain rattle on cold start. Check the service history for evidence of the M274 updated timing chain tensioner being applied. Post-2016 W205 models use the updated M274 specification — significantly lower risk.
  • AIRMATIC suspension failure (C-Class with AIRMATIC option)major
    "Car too low" warning; suspension compressor noise; car sits unevenly; ride height varies after standing overnight
    2014–2021 (W205 with AIRMATIC air suspension option) · From 50,000 miles; risk increases with age (rubber bladders degrade) · £600–£1,200 per air strut; £400–£800 compressor; £200–£400 ride height sensors
    Check: Check whether the car has AIRMATIC air suspension or conventional coil springs (AMG Line and higher trims are more commonly AIRMATIC). If AIRMATIC: walk around the car on level ground and check it sits evenly. Listen for compressor noise on startup. AIRMATIC repairs are one of the highest-cost common fault areas on used W205s. Cars with conventional springs avoid this entirely.
Typical asking price:
£7,895–£19,990, median £12,495 (middle 80% and median, cars on Autoza on 29 October 2026)
Fuel economy:
49–57 mpg (C220d real-world UK motorway); 38–44 mpg (C200 petrol real-world)
Vehicle tax:
£200/year standard rate from the second year, hybrids included — the alternative-fuel discount ended on 1 April 2025. A car registered from April 2017 with a list price over £40,000 when new adds the £440/year Expensive Car Supplement in years 2–6 (£640 in all). Cars registered 2001–2017 pay a CO2 band, roughly £20–£790/year (2026/27 rates).
Best years:
2019, 2021
Used Mercedes-Benz C-Class for saleFull C-Class fault guideUsed Mercedes-Benzes

Also compare:

Which one suits you

Audi A4

Good for: Executive-segment buyers who want a refined, well-built premium saloon or estate. Motorway commuters (A4 Avant TDI is excellent value for high-mileage motorway use). Buyers who will use an Audi specialist for servicing.

Less good for: Buyers who cannot verify the 2.0 TDI timing belt service history. S-Tronic automatic buyers without gearbox oil-service history above 40,000 miles. Buyers wanting the lowest total cost of ownership — a Skoda Superb or Skoda Octavia diesel estate offers broadly similar space and refinement for significantly lower running costs.

Mercedes-Benz C-Class

Good for: Buyers who want Mercedes-Benz prestige and build quality and will use a specialist for servicing. W205 facelift (mid-2018 on) buyers with documented service history. C300e PHEV buyers with home charging who want a premium PHEV at this price point.

Less good for: Buyers looking for the lowest total cost of ownership in the executive segment — main-dealer servicing is expensive. W205 2014–2016 buyers without verified timing chain history on M274 engines. Cars with AIRMATIC suspension without recent AIRMATIC service history.

Frequently Asked Questions

Which is more reliable, the Audi A4 or the Mercedes-Benz C-Class?
Neither stands out on the MOT measure. Their first-time MOT pass rates sit 0.3 percentage points apart once each is compared against the national rate for cars of the same age, which is too close to call (we name a winner only at 2 points or more). A pass with rectification at the station counts as a pass here, and as a failure in DVSA's own initial-test measure. The MOT checks safety and emissions items, not the engine, clutch or gearbox, so this is one measure of how each car holds up rather than a full reliability verdict. Pick on the specific faults each is prone to instead.
How do the MOT pass rates of the Audi A4 and the Mercedes-Benz C-Class compare?
77.3% of Audi A4s pass their MOT first time (24,990 tests in DVSA's records) and 78.6% of Mercedes-Benz C-Class pass their MOT first time (37,418 tests). The national first-time rate is 77.3%, but cars of the Audi A4's age average 75.0% and cars of the Mercedes-Benz C-Class's age 76.0% — so the Audi A4 runs 2.3 points better than its age group and the Mercedes-Benz C-Class runs 2.6 points better than its own. A pass with rectification at the station counts as a pass here, and as a failure in DVSA's own initial-test measure.
Which years of the Audi A4 and Mercedes-Benz C-Class should I avoid?
Audi A4: 2015–2016 B9 launch cars: more reported MMI infotainment issues, some ZF gearbox calibration complaints on early DSG/S-Tronic automatics, and earlier fuel system issues on the 2.0 TDI before production revisions. The DVSA MOT table on this page rates 2016 registrations above all cars registered that year, so it is not named as a year to avoid. Mercedes-Benz C-Class: 2014–2016 launch cars: the most owner reports of M274 timing chain issues, gearbox 7G-Tronic valve body problems, panoramic roof seal leaks and electrical faults. The OM651 diesel used in early C220 CDI also had documented oil leaks from the turbo feed pipe. The DVSA MOT table on this page rates 2014, 2015 and 2016 registrations above all cars registered those years, so they are not named as years to avoid. Judge a C-Class by its registration, service history and the checks below rather than by year.
Is the Audi A4 or the Mercedes-Benz C-Class cheaper to run?
On fuel the two are too close to call: the most economical versions return up to 57 mpg (Audi A4) and 57 mpg (Mercedes-Benz C-Class), on the figures in our model guides. For cars registered from April 2017, vehicle tax works the same way for both: the £200/year standard rate from the second year, hybrids included, plus the £440/year Expensive Car Supplement in years 2–6 on a car that listed at over £40,000 new — the price when new, not what you pay for it used. Any Audi A4 or Mercedes-Benz C-Class registered between 1 March 2001 and 31 March 2017 pays a CO2 band instead, roughly £20–£790/year (2026/27 rates). Insurance differs mainly by driver and postcode rather than by model, so treat any model-level insurance figure with caution.

MOT figures are counted from DVSA records and are the only measured statistic here. Prices, economy and tax bands are indicative and vary by specification, condition and where the car has lived. Last reviewed: 2026-10-06 / 2026-10-06.