You know you’re not living in ordinary times when an automaker touts the gas mileage of its new 510-hp, supercharged V-8, but that’s what Jaguar did when it visited the Autobahn Country Club in Joliet, Ill., with a 2010 XKR coupe and convertible and XFR sport sedan in tow. The event was designed to showcase these models’ performance capabilities to potential customers, but Jaguar let us lowly auto journalists drive both cars, too. The early judgment on the new supercharged V-8? It’s an enthralling blend of power and refinement.