Audi A6 vs BMW 5 Series: which is the better used buy?

On DVSA MOT records the Audi A6 and the BMW 5 Series are level — 0.3 of a percentage point apart once you allow for the age of each fleet, which is too close to separate them. Choose on the fault patterns and running costs below rather than on reliability.

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.

Model	Pass rate	Age-matched national	Difference	Tests
Audi A6	83.1%	76.6%	+6.5	12,504
BMW 5 Series	82.6%	75.9%	+6.8	18,835

Source: DVSA MOT Anonymised Data 2025 (Open Government Licence v3.0). National first-time pass rate 77.3%. Applies to Great Britain — Northern Ireland is tested by the DVA under a separate manual.

Audi A6

C8, 2018–2024 · premium executive saloon

The C8 Audi A6 (2018–2024) is mechanically solid but suffers from MIB3 infotainment freezes pre-2022, DPF blockages on short-trip 2.0 TDI diesels, and Haldex pump wear on quattro variants near 60,000 miles. The 2022 facelift fixed the infotainment. Best-buy years: 2022–2024. Worst: 2018–2019.

What goes wrong

MIB3 infotainment freezemoderate
Screen goes black or freezes on Apple CarPlay / Android Auto; reboot required
2018–2021 · Free under software update; £350–£800 if hardware MMI swap needed
Check: During test drive, connect phone via Apple CarPlay and use it for 15+ minutes. Try switching audio sources. Reproduce the freeze and have it noted on inspection.
DPF blockage (2.0 TDI on short trips)major
Limp mode warning; engine warning light; "DPF full" message
All TDI variants · Mileage-independent — driving pattern matters more · £450–£900 forced regeneration + drive cycle; £1,800+ if DPF replacement
Check: Avoid TDI variants that have only ever done short city trips. Ask about typical journey length. Look for forced-regen events in service history.
Haldex pump (quattro)moderate
Loss of all-wheel drive feel; transmission fault codes; "drivetrain malfunction"
All quattro variants with Haldex (front-biased) · Around 60,000 miles · £450–£700 pump replacement + Haldex fluid service
Check: Service history should show Haldex fluid change every 35,000 miles. Diagnostic scan should show no Haldex codes.
MHEV 48V battery faultsminor
Stop-start system disabled; "Mild Hybrid" warning; reduced fuel economy
2019+ (when 48V system became standard on most variants) · £800–£1,200 battery pack replacement
Check: Test stop-start engagement at every traffic light during drive. Should engage reliably when warm.

Typical asking price:: £16,000–£45,000 (2018–2024)
Real-world economy:: 42–49 mpg for 2.0 TDI; 28–33 mpg for 55 TFSI petrol
Vehicle tax:: £200/year standard rate from the second year, hybrids included — the alternative-fuel discount ended on 1 April 2025. Cars registered 2001–2017 pay a CO2 band, roughly £20–£790/year (2026/27 rates).
Best years:: 2022, 2023
Years to avoid:: 2018, 2019

Full A6 fault guide Used Audis

BMW 5 Series

G30, 2017–2024 · premium executive saloon

The G30 BMW 5 Series (2017–2024) is generally robust in UK conditions, but pre-2018 B47 diesel engines have a known timing-chain weakness above 75,000 miles, and 530d Touring air-suspension can fail after 95,000 miles. Post-2019 examples avoid both issues. Best-buy years: 2019–2021. Worst: pre-2018 diesel.

What goes wrong

Engine — B47 diesel timing chaincritical
Rattle on cold start that fades after 5–10 seconds; metallic chain noise when accelerating
Pre-2018 (B47 engine code, mostly 520d / 525d) · Above 75,000 miles · £2,500–£4,500 (chain, guides, tensioner, gaskets, labour)
Check: Cold-start in person — never accept "the engine is already warm". Borescope inspection at a BMW specialist (£80–£120) is the cheapest insurance.
EGR cooler (B47 diesel)major
Coolant loss with no visible external leak; in worst cases, EGR cooler fire (recall issued)
2014–2018 · Free under recall if not yet completed; otherwise £1,200–£1,800
Check: Ask the dealer for proof the EGR cooler recall was completed. Recall reference: 0036530100. The gov.uk recall checker can verify by VIN.
Air suspension (530d Touring, 540i Touring)moderate
Car sits low at one corner overnight; harsh ride; air-pump runs constantly
All years on Touring with optional air suspension · Typical failure 95,000–110,000 miles · £800–£1,400 per corner (genuine BMW); aftermarket from £350
Check: Park overnight before viewing — check ride height all four corners next morning. Listen for the air pump cycling at idle.
iDrive eDrive battery (530e PHEV)moderate
Reduced electric-only range; longer charging time; loss of full hybrid mode
530e PHEV, all years · After year 5, especially below 30°C usage patterns · £3,500–£6,000 for replacement battery pack
Check: Ask for current EV-only range during test drive. Should achieve 22–28 miles on a full charge in mild UK weather. Below 16 miles signals battery degradation.

Typical asking price:: £12,000–£42,000 (2017–2024)
Real-world economy:: 44–51 mpg real-world for 520d on UK roads (B47 engine)
Vehicle tax:: £200/year standard rate from the second year, hybrids included — the alternative-fuel discount ended on 1 April 2025. Cars registered 2001–2017 pay a CO2 band, roughly £20–£790/year (2026/27 rates).
Best years:: 2019, 2020, 2021
Years to avoid:: 2017, early 2018

Full 5 Series fault guide Used BMWs

Which one suits you

Audi A6

Good for: Buyers prioritising interior quality, long-distance comfort, and quattro all-wheel-drive grip in UK winters.

Less good for: Buyers averse to electronics complexity, anyone who only ever does short city trips (TDI), drivers without tolerance for MIB3 quirks pre-2022.

BMW 5 Series

Good for: Long-distance commuters, motorway drivers, anyone covering 15,000+ miles/year. Excellent depreciation curve from 4 years onwards.

Less good for: Short-trip city driving (DPF issues), drivers who skip routine servicing, anyone unwilling to budget £700–£1,000/year for maintenance.

Frequently Asked Questions

Which is more reliable, the Audi A6 or the BMW 5 Series?

Neither, on the evidence. Their first-time MOT pass rates sit 0.3 of a percentage point apart once each is compared against the national rate for cars of the same age, which is inside the noise. Pick on the specific faults each is prone to instead.

What is the MOT pass rate for the Audi A6?

83.1% of Audi A6s pass their MOT first time, from 12,504 tests in DVSA's records. The national first-time rate is 77.3%, but cars of this model's age average 76.6% — so it runs 6.5 points better than its age group.

What is the MOT pass rate for the BMW 5 Series?

82.6% of BMW 5 Seriess pass their MOT first time, from 18,835 tests. Against the 75.9% that cars of its age average, it runs 6.8 points better.

Which years should I avoid?

For the Audi A6, Pre-2022 infotainment freezes were genuinely dealer-breaking — multiple UK dealers reported buyers returning cars under Consumer Rights Act remedies. Software updates eventually helped but never fully resolved on hardware that shipped in 2018–2019. For the BMW 5 Series, Pre-2018 B47 diesel timing chains are the headline issue — chain stretch above 75,000 miles can cause catastrophic engine damage. Several UK dealers refuse to take pre-2018 520d in part-exchange for this reason.

Which is cheaper to run?

The Audi A6 returns 42–49 mpg for 2.0 TDI; 28–33 mpg for 55 TFSI petrol in real UK driving; the BMW 5 Series returns 44–51 mpg real-world for 520d on UK roads (B47 engine). Vehicle tax: A6 — £200/year standard rate from the second year, hybrids included — the alternative-fuel discount ended on 1 April 2025. Cars registered 2001–2017 pay a CO2 band, roughly £20–£790/year (2026/27 rates).; 5 Series — £200/year standard rate from the second year, hybrids included — the alternative-fuel discount ended on 1 April 2025. Cars registered 2001–2017 pay a CO2 band, 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: 2026-08-14 / 2026-08-14.