There's a fancy new engine under the hood of Land Rover's base Range Rover and Range Rover Sport models. Part of the company's Ingenium engine family, this 3.0-liter inline-six combines a turbocharger, supercharger and 48-volt mild-hybrid system to improve overall efficiency and refinement. In theory, anyway.

This new I6 engine is available with two output levels. The base P360 configuration offers 355 horsepower and 365 pound-feet of torque, while the P400 variant ups those numbers to 395 hp and 406 lb-ft. Both are mated to a smooth-shifting, eight-speed automatic transmission and all-wheel drive, with Land Rover's legendary, go-anywhere capability.

In the case of my Range Rover Sport HST tester, only the more powerful P400 tune is available. HST is a new trim level for the Range Rover Sport; slotting above the HSE, it comes standard with unique 21-inch wheels, LED headlights, red brake calipers and a black exterior visual package, along with a number of interior upgrades including Windsor leather seats, a Meridian sound system and Land Rover's Touch Pro Duo infotainment system -- more on that in a minute.

There's a lot going on under the hood of the Range Rover Sport HST, but it's all in the name of smooth operation. The supercharger provides low-end grunt while the turbocharger supplements higher-range power, and the 48-volt electrical system and 0.2-kilowatt-hour battery work with the standard stop-start system to effortlessly get the Range Rover up and moving.

Does it work? Yes and no. I'm normally the type of person to immediately disable stop-start systems in test cars, but I never turned it off in the HST. Take your foot off the brake at a stoplight and the engine fires up with little noise, vibration or harshness, and power is immediately available. Yet the Range Rover Sport doesn't really, you know, go. The natural reaction is to dial in more throttle input, but then there's a sudden burst of acceleration when the turbocharger wakes up, and you have to lift off the accelerator in order to rein it all back in.

Official EPA fuel economy ratings aren't yet available for the 2020 Range Rover Sport HST, but I'm told the mild-hybrid engine should result in a small improvement over the 17 miles per gallon city, 23 mpg highway and 19 mpg combined ratings of the previous, supercharged V6 model. That's all well and good on paper, but after a week of mixed driving, I never saw a number higher than 18 mpg.

Overall, I'd say the pros and cons of the new I6 engine kind of cancel each other out, making it a wash over the Sport's prior 3.0-liter V6. Thankfully, what hasn't changed is the way the Range Rover Sport handles -- it's still one of the best-driving SUVs in its class. Nicely weighted steering and solid braking feel make the Sport a rewarding SUV to drive. And even when optioned with the larger 22-inch wheels of my test car, the ride quality is nothing short of serene.

Step inside the Range Rover Sport and it's a similar story of serenity. The cabin is as plush as ever, with super comfortable front seats and excellent material quality on every touchable surface. There's ample room in back for two passengers -- three, if you must -- and the Range Rover Sport's upright design pays dividends in terms of headroom. Behind the rear seats, you'll find 27.2 cubic feet of cargo space, and if you fold the second row flat, that area expands to 59.5 cubic feet.

Enlarge Image

Cabin tech is handled by the aforementioned Touch Pro Duo system, Land Rover's latest and greatest infotainment offering. A pair of 10-inch displays on the center stack handle multimedia and vehicle controls, while a digital instrument cluster provides a customizable view of gauges, navigation data, audio information and more.

Much as I like the look of this high-def trilogy, the system is far from perfect. The infotainment screen is pretty easy to navigate, but it's really slow to respond to inputs -- especially upon startup. The screen below it is where you interact with things like vehicle settings (ride height, drive mode and so on) and climate control. While I generally think this touchscreen setup is kind of an answer to a question nobody asked, it's at least straightforward in terms of layout.

Happily, safety tech is in high supply -- if you pay for it, at least. The Sport HST comes standard with a 360-degree camera, traffic sign recognition, lane-departure warning and blind-spot monitoring. If you want to add things like adaptive cruise control, lane-keeping assist and parking assist, you need to pony up for the $4,000 Driver Assist pack. Oh, and one thing to note: The Sport's parking sensors are some of the most sensitive I've experienced in recent memory. You might think you've left enough room between the Range Rover's nose and the back of another car at a traffic light, but the audible beeps say otherwise.

Enlarge Image

Pricing for the 2020 Range Rover Sport lineup starts at $68,650 for the base SE (with the P360 I6 engine) and tops out at $114,500 for the rip-snorting, 575-horsepower SVR. At $82,950, before $1,295 for destination, the HST takes its place right in the heart of the lineup. Of course, that's before you start checking option boxes. Add the aforementioned Drive Assist Pack ($4,000), On/Off-Road Pack ($565), Tow Pack ($1,085), an upgraded sound system ($4,540), carbon fiber exterior accents ($3,500), 22-inch wheels ($1,835), a head-up display ($1,325) and more, and you can get the Range Rover Sport well into six-figure territory. The test car you see here? $105,170.

As for the competition, Mercedes-Benz puts up the best fight with its GLE450 SUV, which also has a mild-hybrid I6 engine. It's a lot cheaper, too, at $61,150 to start, and can be had with Mercedes' superior MBUX cabin tech. Hell, even optioned to the gills, the GLE450 tops out just over $80,000.

There's a ton to like about the Range Rover Sport, though. It's arguably the best-driving luxury SUV in its class, and looks absolutely fantastic from all angles. Plus, thanks to some serious off-road chops, it'll climb a mountain if you ask it to. The new I6 engine doesn't detract from any of this goodness. But it doesn't make the Range Rover Sport any more compelling, either.