We've seen this M40i model's 'B58'-series twin turbo straight six cylinder engine before in BMWs like the M240i and the 440i Gran Coupe and there's lots to like about it. Power output is a healthy 360hp, courtesy of single twin-scroll turbo and variable cam timing technology. And it's mated to xDrive 4WD and an 8-speed paddleshift auto transmission. The 62mph from rest sprint occupies just 4.8s en route to a top speed that has to be artificially limited to 155mph.
You get all of this to the accompaniment of a crisp, muscular soundtrack that's emphasised if you select the provided 'Sport' mode. That opens a flap in the M Sport exhaust which gives you plenty of pops and crackles on the over-run as well as sharper throttle response and more eager kick down. Lowered M Sport suspension with adaptive damping firms up body roll. Plus M Performance-specific variable ratio steering sharpens corner turn-in, while beefier M Sport brakes enhance stopping power. The alternative M40d diesel variant uses a 3.0-litre six cylinder engine putting out 326hp, which is capable of the 62mph sprint in 4.9s.
In keeping with its segment rivals, the exterior looks here are uber-subtle. To the point where many would mistake this car for an ordinary X3 with M Sport trim. Informed loyalist of Munich marque will of course know different, noticing the larger exhausts and the bespoke badging on the tailgate. Other smart touches include bespoke 20-inch M light alloy Double spoke M wheels finished in bicolour Orbit Grey. And a Cerium Grey with black finish for the kidney grille, plus bespoke calipers for the M Sport braking system and Cerium Grey mirror caps.
Inside, apart from a smattering of extra M badges and anthracite headlining, the emphasis on subtlety continues, though you can lift the cabin with options like red leather upholstery. As usual on an X3, the dashtop features the brand's excellent Live Cockpit Professional 10.3-inch infotainment touchscreen which offers crisp, sharp graphics and gesture control. There's plenty of headroom in the back and comfortable space for a couple of adults. Plus you get a decently shaped by 550-litre boot which can be extended to 1,600-litres by folding the 40:20:40-split rear bench.
You won't expect an X3 M40i to be inexpensive and it isn't. BMW wants just over £55,000 for this car; to give you some range perspective, the next conventionally-engined petrol powered model down, the X3 xDrive 20i, costs around £11,000 less, even in top M Sport form. Even the plug-in X3 xDrive 30e variant can he had for well under £50,000. The alternative M40d diesel costs exactly the same as the M40i.
Still, at least standard equipment is generous, with bespoke 20-inch M light alloy Double spoke M wheels, through the spokes of which you glimpse the bespoke calipers of the M Sport braking system. Adaptive damping is standard, as are BMW Icon Adaptive LED headlights with a High Beam assistant. You get electric front seat adjustment with memory buttons, variable sports steering and a man-made Sensatec leather-stitched finished for the dashboard. That's in addition to the features that you'd get with normal M Sport trim that include the BMW Live Cockpit Professional infotainment package that gives you a 10.25-inch centre stack touchscreen. Plus roof rails, sports seats, a semi-digital instrument cluster and LED front fog lights.
Let's get to the WLTP efficiency figures. Those of the M40i are quoted on the combined cycle at between 28.5 and 30.7mpg, with CO2 emissions quoted between 209 and 225g/km. Insurance is group 40E. If the efficiency figures bother you, you'd be better off looking at the alternative M40d diesel. For that black pump-fuelled model, the official combined cycle fuel figures are between 37.2 and 39.2mpg. And the CO2 readings are between 187 and 199g/km.
What else? Well as usual with a BMW, there's a condition-based service indicator on the dash to advise you when your car needs a garage visit. You can check all of this using menus in the 'iDrive' centre-dash display and the car will give you four weeks' notice of when a check-up is needed so you have plenty of time to book it. Less familiar to some buyers will be the clever 'TeleServices' feature that comes as part of the BMW 'ConnectedDrive' services you can access through the iDrive infotainment system. Via this, before each service appointment is due, your X3 can automatically put in a 'TeleServices' call to your nominated BMW service centre, complete with detailed information on vehicle condition. You'll then get a call to arrange a service appointment, something you'll already have budgeted for if, at the point of original purchase, you opted for one of the two fixed cost 'Service Inclusive' or 'Service Inclusive Plus' packages which cover you for five years or 50,000 miles.
My neighbour has an X3 M40i and by all accounts is very happy with it. I'm sure you would be if you chose one. A car this big and tall as always going to slightly struggle in transmitting over 350hp to the tarmac, but this Munich model makes a decent fist of it.
It also has the advantage of being the only model in its class available with a choice of petrol and diesel powertrains - and we'd suggest that for many customers of this model, the alternative M40d black pump-fuelled variant might be a better choice. The M40i though, feels a more bespoke-engineered special product. Even if it's not a proper M car, it's certainly a proper performance SUV.