This is the car Lexus swore they would never make.
Not just any diesel, mind you - it's one of the biggest and most powerful oil-burners on the market. And it's helped make the biggest, most rugged member of the Lexus range - the LX - more capable and sensible than ever before.
Lexus's gargantuan third-generation SUV, based on the legendary Toyota LandCruiser Sahara, has become ever more luxurious and refined with each successive iteration. More equipment, more luxury, more capability. It could take you virtually anywhere on the map and have you stepping out of its leather-trimmed cockpit feeling fresh as a daisy.
The only thing missing was a diesel engine. And with the perfect diesel solution sitting just across the corporate corridor at Toyota, it seemed like a no-brainer. But Lexus held firm - for almost two decades.
Finally, sanity has prevailed. Introducing the long-awaited LX450d. The first and perhaps only Lexus ever to wear the "d" badge on its massive rear tailgate.
Nobody knows why it's taken quite this long - although Lexus has never embraced the high-tech diesels of its European luxury rivals.
Perhaps it's because the LX's prime market is the US, where mammoth petrol-guzzling engines are de rigeur. Perhaps it was to avoid the LX becoming too much like its Toyota LandCruiser corporate cousin.
Whatever the reason, that gloriously smooth and powerful - but frighteningly thirsty - 5.7 litre V8 engine remained the only choice for LX buyers Down Under. Not such a big deal, I suppose, for those people with up to $170,000 to splurge on an oversized, incredibly appointed and immensely capable off-roader.
But a big ask for the rest of us.
The irony, though, is that this new diesel engine instantly makes the imposing LX better in just about every possible way.
For a start, it's cheaper - $135-grand versus at least $20k more for the petrol variant.
It's way, way more economical - delivering an impressive average thirst of just 9.5L/100km, compared to the 14.4L/100km of the LX570.
It's not quite as powerful with its 200kW output - but its rumbling 650Nm of torque are perfect for such a big, heavy machine with the result that the diesel is easier and more effortless to drive.
And it brings just about all of the features of its slightly more luxurious, slightly better equipped sibling - minus some pieces of kit that you're unlikely to miss.
To be honest, the LX570 we tested some months back had so much technology, and so many buttons and dials, that we struggled to take it all in during our week-long test.
The diesel loses a couple of key features - there's not yet a eight-seater model available although that's likely in the new year - but it's every bit as refined, comfortable and high-riding as you might expect from one of these uber-SUVs.
So what's not to like?
Very little, actually.
The Lexus engineers have clearly spent countless hours of extra work reducing the noise intrusion of the big V8 twin-turbo oil-burner - the same engine you'll find in the flagship version of its closely-related Toyota LandCruiser. For the record, the Lexus is appreciably quieter, smoother and better equipped than the Sahara.
The LX450d drives all of that mud-churning torque through a six-speed automatic transmission (the petrol version gets an eight-speeder), and via a sophisticated dual-range, off-road terrain management system that, despite its plush interior, gives the vehicle true go-anywhere capacity.
The addition of a diesel option sets the Lexus clearly apart from its only Japanese challenger - the 5.6-litre petrol V8-powered Infiniti QX80 - and also moves it into the same conversation as leading European options in this class - Audi's very smart Q7, Mercedes-Benz's GL class and the upcoming BMW X8.
And with its trimmed-back price it's likely to drag a few of those buyers back into those shiny Lexus showrooms for a second look at the LX.
This third-generation Lexus has been on the market for the better part of a decade, although it's been facelifted and upgraded a couple of times during that period.
Unlike previous generations that did a cursory job of disguising their Toyota DNA, this one looks and feels every bit a Lexus - with that impeccable build quality and commitment to packing in every possible piece of technology available.
Inside the hushed cabin there's a 12.5-inch colour control screen (with Lexus' clunky mouse-style cursor), premium audio being piped to every corner of the "room", climate controls for each individual passenger and it's all finished in gloriously polished timber and plush, supple leather.
The diesel variant loses a few features inherent in the LX570 - including the 19-speaker Mark Levinson audio and the video screens for rear-seat passengers - ostensibly to save some of the additional weight brought by the big diesel engine.
The 45-litre sub-fuel tank is one of those casualties - although the diesel's frugal thirst means it retains roughly the same 1000km cruising range as the petrol model.
The advantage of losing those third-row seats is that the cargo space is absolutely enormous.
There's no escaping the fact that at almost 3 tonnes, this is a very big and bulky machine - although an array of electronic aides, including active suspension, various stability control devices and a welter of intervention devices, keep it pointing in the right direction, even during sharp turns.
It's almost impossible to reconcile the fact that, just like the most basic LandCruiser model, this Lexus rides on a rugged ladder-frame chassis that, technically at least, should deliver a less car-like ride and handling package.
Forget it. This car feels like luxury through and through. Even with a diesel engine beneath that big bonnet.
HOW BIG? Imagine something the size of a small, Pacific nation - but with a lovely stereo and lovely leather seats. It will also carry almost 1000 litres of cargo without having to put a seat down.
HOW FAST? The low-down torque of the diesel engine gives the LX more get-up than its petrol sibling. But with almost three tonnes to lug around it's still not particularly fast. It gathers speed very efficiently for overtaking, though, and is glorious on a long trip.
HOW THIRSTY? This is where the diesel engine truly shines - with average consumption of 9.5L/100km it uses a full five litres less than the petrol model for every 100km travelled.
HOW MUCH? With a pared-back equipment list, it will set you back $134,500 - representing pretty decent value in this very upper end of the SUV market.