BMW M340i (G20)

The M Performance 3 Series with a straight-six

The BMW M340i xDrive is the six-cylinder, all-wheel-drive M Performance version of the G20 3 Series. This guide is scoped to the M340i xDrive saloon. The Touring (G21) shares the engine and most of the hardware but is a separate body with its own boot and its own, slightly slower, acceleration figure, so it is not covered here. Our catalogue lists a 3.0L turbocharged B58 inline-6 petrol engine producing 369 bhp and 500 Nm, with 0 to 100 km/h in 4.4 seconds, a limited top speed of 250 km/h, an eight-speed automatic gearbox and xDrive four-wheel drive. We have not driven this model for this article. This is a desk-researched ownership guide built from BMW Group's October 2019 UK launch press release, a PistonHeads review of the facelifted car published in September 2022 and the government recall check, with a few clearly named secondary reads where those three are silent. The PistonHeads piece is a driving review and not a used buying guide, because we could not find a PistonHeads used buying guide for this car, so treat its ownership points as a reviewer's observations and not as a fault history.

Checking the figures

BMW's UK release gives the engine as 275 kW and 500 Nm of torque, and labels the power 374 hp. That is the metric horsepower figure, 374 PS, and it converts to the 369 bhp in our catalogue. PistonHeads prints 374 hp at 5,500 to 6,500 rpm and 369 lb ft from 1,900 to 5,000 rpm, which is the same 500 Nm, so an advert that says 374 PS, 374 hp, 275 kW or 369 bhp describes one engine. BMW's release gives 4.4 seconds for 0 to 62 mph in the saloon and 4.5 seconds in the Touring. ADAC, the German motoring club, lists 4.4 seconds for 0 to 100 km/h and 250 km/h for the facelifted saloon, and PistonHeads quotes 155 mph, limited, which is the same 250 km/h. Wikipedia's table shows 4.6 seconds for the M340i, which no manufacturer source we read supports, so we do not use it.

Be careful with a higher rating you may see. BMW's India press kit gives 285 kW and 387 hp, and Wikipedia's engine table also lists 285 kW (387 PS, 382 hp), which is how some markets rate the car. Both the BMW UK release and the ADAC data sheet for the facelifted car show 275 kW and 374 PS, and PistonHeads' 2022 spec box also says 374 hp, so for a UK or European car the catalogue figure applies to both the early and the facelifted car. The weight is 1,800 kg on both PistonHeads' spec box and ADAC's EU figure, which is a heavy car for its output. Confirm the power figure on the registration paperwork of any car you view, and do not assume a rear-drive M340i has the same 4.4 second time, because we found no verified figure for one.

Engine and gearbox

BMW describes the engine as a 3.0-litre straight-six with M TwinPower Turbo technology, and says it added 35 kW and 50 Nm over the engine in the previous range-topping models. The gearbox is the eight-speed Steptronic Sport automatic with paddles and launch control. PistonHeads' facelift review calls the car fabulous to drive, and a PistonHeads forum owner described the B58 with the eight-speed automatic as "pretty flawless", although that is one owner's phrase and not a measured reliability figure. PistonHeads also says a 48V mild-hybrid system was added to the spec sheet in late 2020, so a car built from then on has it, and that it helps the car creep quietly to a stop in town. That means mild hybrid is not what separates early cars from facelifted ones. The facelift review says the engine, gear ratios and mild-hybrid system were otherwise carried over, and adds an M Boost function that drops to the lowest gear with an extended pull of the left paddle, plus a new gear-selection toggle that must be moved to S before the paddles work manually.

Reliability evidence is thin. In a PistonHeads forum thread from February 2023, one 330i owner reported replacement of the PCV system, a turbo and the plastic oil filter housing, and a recurring catalytic converter efficiency code, but the thread does not say these affect the M340i, and another poster said M340i owners did not seem to have these problems. We treat those as checks to make on any B58 car, not as known M340i faults. Ask for a service history with oil changes at sensible intervals, look for oil or coolant seepage around the engine, and have the car scanned for stored fault codes.

Chassis, brakes and wheels

The xDrive system uses an electronically controlled multi-plate clutch in the transfer case, rear-biased and working with the stability control, and an electronically controlled, fully variable rear locking differential is standard. PistonHeads says xDrive has no rear-drive-only mode in this car, unlike the M3, and that the reviewer did not miss it. The M Sport suspension lowers the ride height by 10 mm and comes with variable sport steering, while Adaptive M suspension with electronically controlled dampers was an option, so confirm which car you are viewing. A 2018 PistonHeads prototype drive, on a circuit only, described stiffer, shorter springs, stronger anti-roll bars and more negative front camber, and said the adaptive dampers might not have all the answers on a bumpy road given the weight.

BMW lists four-piston fixed front calipers with 348 mm discs and single-piston floating rear calipers with 345 mm discs, with blue calipers carrying the M logo. Standard wheels are 18-inch with mixed-size tyres, 225/45 R18 at the front and 255/40 R18 at the rear, with 19-inch wheels as an option. ADAC lists the same tyre sizes for the facelifted car. Because front and rear sizes differ, tyres cannot be swapped between axles to even out wear, so check each tyre separately for uneven wear that could point to alignment problems, and inspect the wheels for kerb damage. Look at disc surfaces for lipping and at the pads, and test the brakes hard enough to check for pedal feel and pulling.

Body, interior and electronics

The saloon has an M front apron, side skirts, a mesh-design kidney grille, trapezoidal twin tailpipes and a body-coloured M rear spoiler. ADAC lists a 480 litre boot. Inside, BMW's launch specification includes Sensatec and Alcantara sports seats with blue contrast quilting, an M leather steering wheel, an anthracite headliner, three-zone climate control and front and rear parking sensors. BMW also made a limited First Edition of 340 saloons and 340 Touring cars from November 2019, so a car advertised as a First Edition should be checked against its paperwork.

The biggest difference between early and facelifted cars is the cabin technology. The 2019 UK specification has the Live Cockpit Plus with an 8.8-inch display and Connected Package Plus. PistonHeads says the facelift brought a curved touchscreen running BMW Operating System 8, removed gesture control, moved the climate controls into the display, added Amazon Alexa and made it fiddlier to turn off lane-keep assist and select the sportier stability setting. It also says the sound feature is switched off through the same menu. Whichever version you view, test every screen function, the cameras and sensors, the driver assistance functions and any connected services, and ask what is active on the account.

Recalls and history

We did not find a UK recall list for this model from BMW or DVSA that we could read. A third-party aggregator, car-recalls.eu, lists a European Safety Gate alert (number 44/2025, published at the end of October 2025) covering M340i vehicles with the B58 engine built between 20 March 2018 and 11 February 2025, for an engine starting motor whose electrical contacts may overheat, with a possible fire risk. That page lists the G20 type code as the US version, does not state a remedy, and says the recall may not apply to every car, so we cannot say it covers a particular UK car. Enter the registration in the DVSA vehicle recall service and ask a BMW dealer to check the VIN for open campaigns, and ask the seller for paperwork showing any work done. Also ask for the full service history, any accident repair evidence and a list of modifications, especially remaps, which can change the tune and the paperwork figures.

Buying decision

PistonHeads' verdict on the facelifted car is that it remains a fabulous car to drive, and the reviewer calls it an ideal everyday sports saloon or estate for someone not ready to plug in at home, while noting that it feels like a big, heavy car these days and that the 330e plug-in offers similar performance with much lower running costs. BMW Blog reported on 26 September 2026 that the G20 ends production in October 2026, with the next 3 Series due to start production in Dingolfing in November and its M350 successor getting more power from the same B58. That report is a pre-announcement from a secondary source and we found no official end-of-production date, so check availability with a dealer. Both early and facelifted cars appear in used adverts, so compare current adverts instead of relying on a price quoted here. Prefer a car with a documented service history, matching tyres in good condition, a clear recall record and the screen generation you can live with.