If you see an “R” in a Jag’s nomenclature, you’re in for a good time. Under the long louvered hood of the XKR rests a supercharged 4.2-liter V8 engine that produces 420 horsepower and 413 lb.-ft. of torque. Routing that power to the rear wheels is a six-speed automatic transmission with manual control through paddles mounted on the steering wheel. The thrust is prodigious, pinning you in your seat as the automatic shifts effortlessly. Use the paddles and it matches revs on downshifts, blipping the throttle with the expertise of a Formula 1 driver. Shifts are harsher in manual mode, and the transmission upshifts redline in either mode, but otherwise this is an excellent powertrain that also netted us 15.6 mpg.