Audi A4 B9 used: the engine and year that age best

The Audi A4 B9 used saloon and Avant span roughly £12,000 to £28,000 in 2026, and the buy is a post-2019 facelift 40 TDI or 35 TFSI with full Audi history. The pre-2018 petrols are the ones to vet hardest.

What the B9 generation actually is

The B9 A4 ran from 2015 to 2023 in saloon and Avant estate forms, with a significant facelift arriving for the 2020 model year (cars registered from mid-2019). It sits on the Volkswagen Group MLB Evo platform, which is why it shares so much hardware with the larger Audi A6 C8 executive saloon and the Audi Q5 FY. The early cars wore the cleaner, more rounded nose; the facelift brought sharper bumpers, a flatter Singleframe grille, standard LED headlamps and a larger 10.1-inch MMI touchscreen that replaced the old rotary-dial system. For a used buyer that split matters: the facelift cabin is the one that feels current, and it is the one we would target first.

35 TFSI, 40 TFSI, 35 TDI or 40 TDI: the engine to buy

Audi renamed the range to power-output badges partway through the run, which confuses used listings. In plain terms: 35 TFSI is the 150PS 2.0 petrol, 40 TFSI the 190PS (later 204PS) 2.0 petrol, 35 TDI the 163PS 2.0 diesel and 40 TDI the 190PS 2.0 diesel with quattro on most cars. All use versions of the EA888 (petrol) or EA288 (diesel) family. For a high-mileage motorway driver the 40 TDI quattro is the sweet spot: real-world economy in the high-40s mpg, strong mid-range and the eight-speed torque-converter automatic rather than the dual-clutch. If your mileage is lower and mostly urban, the 35 or 40 TFSI petrol sidesteps the diesel particulate filter headaches that dominate owner complaints. We would avoid the entry 1.4 TFSI early cars on resale grounds; the volume of better 2.0 examples makes them hard to recommend.

EA888 health and the faults that bite by year

The B9’s 2.0 TFSI petrol uses the third-generation EA888, a notably better unit than the oil-burning B8 engine it replaced, with revised piston rings and an updated chain tensioner. The caveat owners stress on Audi-Sport.net is that the earliest pre-2018 cars can still show a weaker timing-chain tensioner, so on any 2016 to 2017 petrol you want evidence the tensioner has been checked or replaced and that oil changes were on the shorter interval. Across both fuels the recurring high-mileage items are MMI infotainment faults, water-pump failure, worn front control-arm bushings and, on the diesels, DPF regeneration trouble on cars that only ever did short urban hops. None of these are generation-killers; they are negotiating points. A documented water-pump and tensioner history on a 70,000-mile car is worth more than a slightly lower asking price on a thin-history example.

The S4: from petrol to diesel and back

The performance S4 has an unusual engine story that catches buyers out. The pre-facelift B9 S4 (2016 to 2019) ran a 3.0-litre single-turbo petrol V6 with 349bhp, good for 0 to 62mph in 4.7 seconds. Audi then pulled it during the WLTP emissions reforms and the 2019 facelift S4 arrived in the UK and Europe as a 3.0 TDI diesel V6 with 342bhp and a huge 700Nm of torque, paired to a mild-hybrid system, per the RAC’s used S4 review. Other markets such as the US kept the 3.0 TFSI petrol S4 throughout the run. For a UK used buyer that means you must read the S4 listing carefully: a 2017 car is the petrol, a 2020 car is most likely the torque-rich TDI. We rate the diesel S4 as the better everyday choice for its 40mpg-plus reach; the petrol is the one enthusiasts will chase. Either way it is a discreet alternative to a BMW 5 Series G30 for someone who wants pace without shouting about it.

S tronic versus manual, and the Virtual Cockpit question

Most B9 A4s you will see are automatics. The diesels and higher petrols use either a seven-speed S tronic dual-clutch or, on the 40 TDI quattro, a smoother eight-speed torque-converter automatic; the lower front-wheel-drive cars tend to get the S tronic. Owner sentiment on the S tronic is broadly positive on the open road but flags occasional low-speed jerkiness, so budget for a transmission service if the history is silent on it. A six-speed manual exists on early lower-powered cars and is rare; it is the purist’s pick but cuts your resale audience. On equipment, the Virtual Cockpit digital instrument display is the feature owners single out as transforming the cabin, and Technik and S line trims usually carry it. We would prioritise a car with the full Virtual Cockpit and the larger MMI screen over a base-spec example with a bigger discount.

Audi A4 B9 used prices and what your budget buys

In 2026 the B9 spans a wide band on the UK classifieds. Around £12,000 to £15,000 buys an early 2016 to 2017 saloon, typically a 2.0 TDI or 35 TFSI with 60,000 to 90,000 miles; this is the value end where history checking matters most. The £16,000 to £21,000 middle is where the facelift cars start, and it is the band we would shop in: a 2019 to 2020 40 TDI quattro Avant or a 35 TFSI S line saloon with full Audi service history. Above £22,000 to £28,000 you reach the freshest 2021 to 2023 cars and tidy S4 examples (figures from an Auto Trader inventory scan, June 2026). If you are weighing the A4 against rivals, our take on the Mercedes C-Class W205 covers the closest direct competitor, and the same money in the executive class opens up genuine cross-shopping.

Pre-purchase checks before you commit

Run the basics first: an HPI check for finance and write-off history, the gov.uk MOT history for advisories that recur (suspension arms, tyres worn unevenly hinting at geometry issues), and the gov.uk DVSA recall checker against the VIN. On the test drive, work the MMI system through Bluetooth pairing and the reversing camera, listen for a cold-start rattle on petrols (tensioner), and feel for clean low-speed shifts from the S tronic. Confirm the cambelt or chain service position for the engine, check the diesel has not lived a short-trip life if it is a DPF car, and insist on stamped or digital Audi service history. An Audi Approved used warranty adds twelve months of cover and is worth paying a small premium for on a higher-mileage example. If the paperwork is thin, walk; there are hundreds of better-documented B9s on sale.

Running costs, insurance and depreciation

The B9 is cheap to run by executive-saloon standards, and it scores well against the rivals in our wider used premium buying guides. The 2.0 TDI diesels return high-40s mpg in real use, the petrols low-to-mid 40s; insurance groups sit broadly in the high-20s to low-30s for mainstream A4s, rising for the S4. Servicing at an Audi main dealer is dearer than an independent specialist, and for an out-of-warranty B9 a VAG-specialist independent is the value play. Depreciation has already done its worst on the early cars, which is the whole appeal of buying used here: the steep first-owner loss is behind you, and a well-bought facelift car holds its money far better than a new one would. For the bigger-saloon alternative if your budget stretches, the Audi A8 D5 shows how much luxury depreciation can hand a used buyer, though running costs climb with it.

Our take

If you want a calm, well-built executive saloon or estate that has already taken its depreciation hit, the Audi A4 B9 used is one of the most sensible buys in the class. Our pick is a 2019-to-2021 facelift 40 TDI quattro with full Audi service history at £18,000 to £22,000: the torque-converter automatic is smoother than the dual-clutch, the diesel suits the high-mileage life these cars are bought for, and the facelift cabin with Virtual Cockpit still feels current. Lower-mileage urban drivers should take a 35 or 40 TFSI petrol instead to dodge the DPF trouble. The car to vet hardest is the pre-2018 petrol with a silent service book, where the timing-chain tensioner is the unknown. Walk away from thin paperwork and you will own one of the safer used premium choices on the market. The S4 is a discreet bonus for anyone who wants the pace.