2018 Bentley Bentayga Diesel

It hasn’t been long since the very idea of a diesel-powered Bentley SUV would have been regarded as the sort of heresy that gets angry mobs lighting up their flaming torches and heading for the creepy castle. Yet the Bentley Bentayga diesel is a thing—albeit one that will be denied to us—and after driving it in the United Kingdom, we can report that the new engine suits the luxurious beast almost perfectly.

Meant for America, until . . .

The delay between the time an automaker signs off on an investment and the fruit of that spending reaches the market plays a vital part in this oily Bentayga’s story. The triple-boosted V-8 TDI originally was meant to come to North America in the Audi SQ7 that shares it, and it was engineered to meet all appropriate federal standards. But then Dieselgate happened, and the Volkswagen Group decided that none of its brands would sell any more compression-ignition engines on this side of the Atlantic. So the Bentayga diesel finds itself on the long list of Awesome Cars Unfairly Denied Us.

This is a shame, mostly because this might well be the greatest compression-ignition engine ever fitted to a passenger vehicle. Technically, the propulsion unit is identical to that in the Audi SQ7, meaning that it’s a V-8 displacing 4.0 liters and has sequential turbochargers that use a clever variable-valve system to bring the second turbine on boil. These are further assisted by a 48-volt electric supercharger which, basically, is a 9-hp motor that sits downstream of the intercooler and can spin a centrifugal-flow compressor up to 70,000 rpm in less than a quarter of a second to reduce turbo lag to the barest level of detectability.

The result is an engine with a character akin to that of the old turbocharged 6.75-liter pushrod gasoline V-8 that Bentley formerly installed in cars such as the Arnage. Like that six-and-three-quarter-liter engine, the TDI isn’t built to rev, although it pulls cleanly to its limiter at 5000 rpm. It does generate enormous low-down torque, delivering the peak 664 lb-ft over a wide band starting at just 1000 rpm.

Yet the diesel also manages to be more refined than its gasoline grandfather ever was, emitting nothing louder than a purposeful growl even under the hardest use. The biggest difference is fuel economy, which is unlikely to be much of an issue for anyone with the considerable wherewithal needed to fund any Bentayga purchase, but it’s still a neat party trick. If this were certified by the EPA, we estimate it would get about 26 mpg on the highway—a figure that, in conjunction with the 22.5-gallon fuel tank, gives the Bentayga diesel a range that can fairly be described as Continent crushing in terms of geographic reach.

The torque peak is identical to that quoted for the W-12 version, although that’s more likely electronically limited by the limits of the eight-speed automatic transmission rather than a spooky coincidence. While the diesel is significantly deficient in power by comparison—its 429-hp rating is 171 shy of the W-12’s output—it lacks little in real-world pace. Or, indeed, absolute speed: Bentley quotes a 4.6-second zero-to-60-mph time. (We recently ran the W-12 model to 60 mph in 3.6 seconds against a claimed 4.0 seconds to 60.) The diesel’s top speed of 168 mph likewise is some way off the W-12’s 187 mph, but we suspect that owners will rarely feel the lack. It’s also worth noting that we experienced none of the surging or lag we detected when we tested the W-12; on everything except cylinder count and peak output, this is the better engine.

Ride and Handling? Check!

The rest of the dynamic experience is close to that of the 12-cylinder model. Driving manners are exemplary, with the air springs and adaptive dampers delivering a ride quality that isn’t quite as imperious over bumps as that of the Q7, though cruising refinement is good enough to make you suspect hearing loss. The Bentayga is capable of generating ample grip when called upon to do so (in our test of the W-12, we measured 0.85 g on the skidpad), and it is surprisingly playful near the limit. Responses are linear and accurate, although there’s never any doubting the Bentayga’s mass.

Bentley says the diesel is slightly heavier than the W-12 thanks to the iron block and the additional supercharger. All those pounds become most obvious when slowing down—or, rather, when not. The gearbox has a sail mode that declutches when the car coasts, and the Bentayga feels as if it could roll several miles on nothing more than its own momentum. We experimented with using the transmission’s manual mode to lock it into eighth gear, which created a far more natural-feeling deceleration curve but also proved that the engine will pull cleanly from just 1000 rpm.

Subtlety Not an Option

While the Bentayga’s interior feels appropriately special, especially when trimmed with the combination of tan leather and light woodwork that only the British seem capable of pulling off, the exterior design still is likely to divide opinion. The Bentley’s visual mass seems somehow larger due to the acreage of chrome grille and a not entirely successful attempt to add Continental GT–style muscle to the rear haunches. A close inspection reveals some surprisingly proletarian touches, including a couple of exposed screw heads in the front bumper’s lower intake grille.

The infotainment system also deserves some mild chiding. It’s a Bentleyized version of the previous-generation Audi system, and although entirely adequate it feels old and somewhat clunky. Strange that the $200,000 car that sits at the top of the Volkswagen Group’s SUV hierarchy has a system that’s inferior to the one in its $100,000 cousin. The new Continental GT is switching to a version of Audi’s current class-leading MMI, so it is likely the Bentayga will follow shortly behind.

In future years, Europe’s current love for diesels likely will be seen as a historical blip; even before the scandal, diesel emissions standards were tightening, and sales had begun to decline. The controversy, of course, dramatically sped up the process not only in America but in many other countries where diesel was once considered the answer for reducing carbon emissions. It’s unlikely that any automaker will ever devote the considerable funds necessary to create a better diesel engine, meaning that the Bentayga diesel’s position at the very top of the tree probably never will be challenged.

Specifications >

VEHICLE TYPE: front-engine, all-wheel-drive, 4-, 5-, or 7-passenger, 4-door hatchback

BASE PRICE (U.K.): $153,000

ENGINE TYPE: sequentially turbocharged, supercharged, and intercooled DOHC 32-valve diesel V-8; iron block and aluminum heads; direct fuel injection

Displacement: 241 cu in, 3956 cc
Power: 429 hp @ 5000 rpm
Torque: 664 lb-ft @ 1000 rpm

TRANSMISSION: 8-speed automatic with manual shifting mode

DIMENSIONS:
Wheelbase: 117.9 in
Length: 202.4 in
Width: 78.7 in Height: 68.6 in
Passenger volume: 109 cu ft
Cargo volume: 15 cu ft
Curb weight (C/D est): 5800 lb

PERFORMANCE (C/D EST):
Zero to 60 mph: 4.2 sec
Zero to 100 mph: 9.5 sec
Standing ¼-mile: 12.6 sec
Top speed: 168 mph

FUEL ECONOMY (C/D EST):
Combined/city/highway: 26/24/31 mpg