In many ways, the Cadillac CT6 Plug-in Hybrid is the most interesting car the brand sells. Despite having a turbocharged four-cylinder hybrid powertrain, it makes the most torque of any CT6, even the twin-turbocharged V6 model. It also has a claimed electric range of 31 miles and can still manage a combined fuel economy of 26 mpg with just the gas engine. Even its origin is interesting, since its final assembly point is China. To cap things off, it's also the second most expensive CT6 in the range. To find out if the CT6 is worth that money, and has more to offer than fun facts, we spent some time behind the wheel.Editor-in-Chief Greg Migliore: I achieved 34.1 miles per gallon for my roughly 14-mile roundtrip in the CT6 hybrid. This sedan is a rolling example of where Luxury is heading in the near term: Existing models souped up with hybrid tech, and the green features will go along way toward keeping big sedans like this relevant. It's a smart play for Cadillac to add a product like this.Otherwise, it's a fairly standard-issue CT6, which is a solid car. The flashy head- and taillights look great. The design is angled, creased and nicely proportioned. The interior is comfortable and roomy. It's a nice car. Cadillac invested a lot in the CT6, and it shows. Rumors have long swirled that the brand will add a larger flagship, though in this climate, that's hard to envision. For now, the CT6 does the job as Cadillac's standard bearer.Associate Editor Joel Stocksdale: Of all the different CT6 variants available, the CT6 PHEV is the one I would pick for myself. Why? Because the hybrid powertrain finally delivers on the quiet, refined driving experience I want from a flagship luxury sedan. I was a bit surprised by this, too, since the gas engine under the hood is the 2.0-liter four-cylinder used elsewhere, which isn't the smoothest thing in the world. But assist from the electric motor helps keep the four-cylinder from having to wind up too much to move the big Caddy, and when the gas engine does rev hard, it's well muffled by whatever insulation is in the car.Besides aural refinement, the power delivery is oil-on-ice slick. The blending of electric and gas power is seamless. There's no waiting on the turbo to spool up, and there's no loss of power at higher rpms with the electric motor. They work in perfect harmony providing excellent low-down grunt and solid upper-end power. The transmission is super smooth, too allowing for happy wafting wherever you go. I was also pleased to find that the "manual" mode on the transmission actually sets how aggressive the regenerative braking is, and you can make it darn near as aggressive as a Chevy Bolt EV. It's not quite one-pedal driving, but pretty close. And driving enthusiastically is actually fun in the CT6 because the car drives like a car half its size. It's responds quickly and enthusiastically to the steering and feels very planted. The car stays pretty flat, too, though the trade-off is a firm ride. The brakes feel mostly good, also. They feel firm and progressive, but a little grabby at low speeds.