Land Rover Diesel Engines: First Drive

More than just the most recent manufacturer to introduce diesel engines in its U.S. models, Jaguar Land Rover Automotive has vowed to provide diesels for all of its models except the Jaguar F-Type coupe and roadster. The first such engine is now available in Land Rover’s 2016 Range Rover and Range Rover Sport — different models, though they’re easily mistaken as one. I drove both versions on and off-road.

Luxury brands try to keep their diesel engines quiet, but I’ve never experienced one as unobtrusive as the 3.0-liter turbo-diesel V-6 in these models. You can hear the telltale clatter better if one accelerates past you, but if it’s just idling next to you or you’re inside, driving it, you rarely pick up on anything to distinguish it from the supercharged gas V-6 that’s the closest in cost and output.

Credit belongs in part to the Range Rover models’ already excellent noise isolation, which gives them a quieter cabin at high speeds than a giant box has any right to exhibit. Land Rover held a few consumer clinics around the U.S. at which the vehicles weren’t identified as diesels, and the company says not a single participant picked up on it. I believe it. I smelled some diesel exhaust a couple of times when plodding over desert trails outside Sedona, Ariz., at a pace the speedometer couldn’t register, but one could easily have attributed that to a nearby vehicle if driving in normal traffic.

According to Land Rover, the Range Rover Sport does zero-to-60 mph in 6.8 seconds with the gas V-6 and 7.1 seconds with the diesel, and 7.0 and 7.4 seconds, respectively, for the heavier Range Rover.

Endowed with the diesel’s 440 pounds-feet of torque at 1,700 rpm, both the Range Rover and Sport bolt off the line, their standard four-wheel drive and big tires wasting no power. As expected, however, the engine’s 254 horsepower makes for modest passing power at highway speeds compared with the gas version, which boasts 340 hp but just 332 pounds-feet of torque at 3,500 rpm. In the middle driving range, the lopsided specs sort of even out. At most, the diesel lets the eight-speed automatic transmission chill a little on hilly roads where the gas V-6 would have to shift more often.

Likewise, the diesel versions of both SUVs clamber more effortlessly over off-road obstacles than does the gas V-6, but the supercharged V-8-powered models have the best of both worlds with 510 hp and 461 pounds-feet of torque at 2,500 rpm.

The diesel is sized right — to provide a satisfying driving experience while burning less fuel: an EPA-estimated 22/29/25 mpg city/highway/combined versus the gas V-6’s 17/23/19 mpg on premium (figures are the same for the Range Rover and Range Rover Sport). According to AAA, the national average price per gallon of diesel is $2.31 as I write this. Regular gasoline is $2.00, but the gas-powered Land Rovers require premium, which is currently $2.50. The advantage is clear.

In the big picture, there aren’t many differences between these models’ diesel and gas V-6 versions. They have the same transmissions with the same gearing, just a taller final drive ratio for the diesels. Their curb weights are within 50 pounds of each other, and the tow rating is identical: 7,716 pounds. Even the primary maintenance intervals are the same: 16,000 miles or 12 months for oil changes, though the Td6 also requires diesel exhaust fluid that gets refilled on the same schedule.

One difference is the price: $1,500 more for the diesel in all cases. Not bad at all compared with direct competitors and the automotive market as a whole: BMW charges the same premium for the diesel upgrade in the BMW X5 with all-wheel drive, and the diesel Mercedes-Benz GLE-Class is just $1,100 more than the comparable gas version, while the Chevrolet Colorado midsize pickup truck’s new diesel comes at a $3,730 premium available only on higher trim levels. Conversely, the Land Rover diesel, designated Td6, comes in the most-affordable trim levels: the Sport’s SE and HSE and the regular Range Rover’s base and HSE versions.

A couple of innovations in the Td6 are notable, including the employment of a misfueling device at the fuel-filler opening designed to prevent accidental gasoline fueling instead of diesel. Where the larger-diameter diesel-pump nozzle prevents the opposite, there’s usually nothing to prevent the skinnier gas nozzle from being inserted into a diesel filler. Land Rover’s solution is a butterfly valve recessed a bit in the filler tube that moves out of the way only when a larger-diameter nozzle presses on a collar at the opening.

Also, the Td6 engine uses a low-pressure version of an exhaust-gas recirculation circuit (a common emissions-control device) that pulls exhaust from downstream of the particulate filter and routes it to the turbocharger inlet. In most diesels, the EGR circuit routes hot, high-pressure exhaust from the exhaust manifold to the intake manifold. The Land Rover system’s cleaner exhaust gets intercooled along with the intake air, resulting in lower combustion temperatures and less oxides of nitrogen, a pollutant for which diesels are notorious.

Land Rover predicts the Td6 will account for roughly 15 percent of Range Rover and Sport sales, though fuel prices — low and high — are sure to influence the new engine’s appeal. The general view is that people who buy luxury SUVs “don’t care about fuel costs.” Granted, they may be in a better position to absorb that cost, but I suspect they’ll care if a substantially more efficient option comes at just $1,500 more, with no real tradeoff. That’s what the Td6 Range Rovers represent.