Review: BMW M340i xDrive, is this the four-door Toyota GR Supra?

Jason · Jan 07, 2021 11:00 AM

Every so often, there are cars that cross our paths and leave an indelible mark in our motoring journey. We have been rather fortunate in the past few weeks, having sampled the Porsche 718 Cayman GT4 and now, the BMW M340i xDrive. Not one, but two cars powered by 6-cylinders? Happy days.

BMW and 6-cylinders, a love story like no other

I used to tell people, don’t bother buying a BMW unless it’s a 6-cylinder (which obviously sounds rather daft now). You see, Munich’s finest cars have, more often than not, possessed of a 6-cylinder heart. Alas, the downsizing trend happened and even BMW had to succumb to using 4-cylinder powerplants (the B48 is a pretty good engine, though). What remains true, is that BMW still makes the finest 6-cylinder engines on earth.

Exterior - just special enough over a 330i, yet still subtle

From a distance, it's really hard to spot a M340i over a 330i. Go closer and the differences are obvious but subtle. In front, the BMW Laser Light has a different DRL signature, the kidney grille gets a swankier design (finished with a light bronze trim that also extends to the wing mirror caps). 

Above: M340i LED DRLs have a distinct signature

The M340i also gets a gorgeous set of 19-inch Style 792 M wheels, which I absolutely adore. At the rear, the rear bumpers of the M340i is finished off with trapezoidal exhaust exits, and they do just enough to lift the M340i's road presence. 

Interior - feels higher quality than its stablemates

Inside, the overall design architecture is largely the same as its G20 siblings, although the various touchpoints somehow felt more high quality. It wasn't just one of us who noticed it, so it definitely wasn't an anomaly. I did find the rim thickness of the M Sport steering wheel to be a bit much. Don't get me wrong, it looks and feels lovely, but the rim is just way too thick to get a proper grip.

Perfectly liveable rear quarters

The M340i nails the 4-door sedan brief with ease, with ample leg and headroom to fit 4 adults comfortably. The cabin is well-built, refined and quiet (our tests recorded an impressive 65 dB at 110 km/h). Driving position is as good as can be. Another nifty feature is wireless Android Auto and Apple CarPlay, which is integrated to the fully-digital instrument cluster and infotainment system, which takes some acclimatising as it's not the most intuitive to use.

Are digital displays too much of a good thing? Read on

Driving experience - more GT than GTS

Which brings us nicely to the reason why we’re here, the B58 3.0-litre straight-six in the M340i. 387 PS500 Nm and a claimed 0-100 km/h sprint in 4.4 seconds (although our testing consistently returned 4.7 seconds) are the headlines here, but it is the manner of how it serves up the shove available that makes it oh-so-compelling. Smooth, creamy, crisp, sonorous, glorious (I could go on).

Is there a better 6-cylinder than the B58?

There’s a majestic and well-oiled precision to how this engine responds to the demands of your right foot. It’s perfectly tractable and benign when cruising, but when you summon it, it makes the most wonderful howl, with very little turbo lag. How is it that BMW has managed this in a turbocharged engine?

The B58 is expertly partnered by the ZF 8-speed automatic. I cannot say enough good things about this transmission. Again, it’s happy to slur shifts when you’re taking it easy, but just as able to deliver rapid-fire gearchanges when you up the ante. It’s no exaggeration to say that this is THE BEST automatic transmission out there right now. It makes dual-clutch transmissions redundant - it’s that good.

So far, so good right? This is a 3-series, a sports sedan, it’s gotta drive well, right? Well, if you spend most of your time on the expressways, then the M340i does a sterling job. The B58 feels like it has an endless reserve of power. It takes high-speed sweepers without breaking sweat. Cross-country pace is eye-widening.

It is on smaller, tighter roads that the chassis starts to unravel. It doesn’t like to be hustled along B-roads, where there’s plenty of technical demands and direction changes. This is even after dialling in the most aggressive driving modes. Turns out, its biggest problem is its weight.

If there's one car that didn't need xDrive, it would be the M340i

At 1,745 kgs, (the M340i has xDrive, which also adds weight) it’s very lardy, and you feel every bit of it when you ask it to dance. The A90 Toyota GR Supra, which has an identical powertrain, is 175 kilos lighter, and it feels much more agile than the M340i (of course, being lower helps).

Gorgeous 19-inch Style 792 M wheels

Braking performance, whilst adequate, does suffer when you batter it, again because it’s inherently a heavy car. Our internal testing (100-0 km/h) returned a best result of 35.7 metres. In my honest opinion, xDrive isn’t necessary in this instance, as the difference it brings isn’t significant enough.

Ride comfort - plush, accomplished and comfortable, but no lumbar adjustment

No lumbar support adjustment here

The adaptive damping does a top job in Comfort mode, soaking up bumps and ruts with consummate confidence, considering it's riding on 19-inch wheels. The seats are pretty good, offering enough adjustments for a guy of my size. One glaring ommision is the lack of lumbar support adjustment. In a car costing this much, that is criminal.

The damping in Sports mode is something reserved for the most smooth tarmac surfaces. Even during higher-speed testing, I left the suspension in Comfort mode. It was just at odds with the rest of the car, pogo-ing to a very disconcerting degree. 

Fuel consumption - not great, but not woeful either

Fuel consumption is very respectable for the performance on offer, returning 12.4l/100km. This figure was achieved through a combination of high-speed cruising, city-driving and our internal sprint tests. Calculations were made over a distance of 166 km. 


If I have to live with just one engine for the rest of my life, this would be the one. That’s how highly I rate it. If you’re after a sharp, lithe machine, look elsewhere. The M340i xDrive is more at home munching miles rather than canyon-carving. My ideal spec for this car? Do away with the xDrive, save some weight and add some agility. Perfection, in the form of a 4-door Toyota GR Supra.

Long snout, short tail, classic sports sedan proportions