Just last weekend we were drawing up our list of favourite diesels, and it came as a surprise to precisely nobody involved that BMW featured on the list prominently. For more than 20 years now, stretching back to that groundbreaking E46 330d and perhaps even further, the manufacturer has been at the forefront of mating diesel innovation with driver reward. Cars like the 123d, 335d (especially when mapped), 535d and 640d showed that diesel could really be actively desirable and perfectly suitable for BMWs. Don't forget the success that Alpina enjoyed with black pump Buchloe bruisers, either. It was a valid alternative.
Therefore, however understandable it is in the current climate, that BMW has ceased production of its M50d quad-turbo straight-six diesel is something of a shame. Because it was a momentous powerplant, the perfect fit for the burly BMWs in which it was installed. The B57S was everything you'd want from a modern diesel, with a great vat of torque (561lb ft) available from next to no revs, a fair willingness to rev and a soundtrack that, if discernibly diesel, was certainly still straight-six smooth, too. Like a hydroelectric dam almost, you couldn't help but admire the diesel as a formidable feat of engineering - even if it wasn't something to fall head over heels in love with. In any of the cars the engine was available in - X5, X6 and X7 in the UK - it was hard to think of better long-distance transport.
But that era is done now, European production for the M50d models having come to an end as BMW has "reviewed and refined" its range in order to "reflect customer preferences". Diesel simply doesn't have the popularity it once did, and seems unlikely to ever reach anywhere near those heights again. Combine that downturn with the complexity that inevitably comes with putting four turbochargers in a three-litre diesel, and the B57's fate was inevitable. Which, for all the fuel's bad press, is sad news, because it really was the perfect accompaniment in those SUVs. Those tempted by the idea of quad-turbo diesel (and it really is as mighty as it sounds) should know that used M50ds start at £55k for cars like this X5. Something to experience while you still can.
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