It's common for a sports car's engine to sit between the passenger compartment and the rear weels; this "mid-engine" layout centers the car's mass, making it nimbler. Traditionally, luxury cars were too slow to benefit from a mid-engine layout, but not Peugeot's latest concept: a four-door luxury sedan with the same 700hop V-12 as the company's next LeMans racecar, placed in the same spot. In addition to giving the sedan the road-holding ability of a racecar, there's less noise, becuase you're driving away from the engine's growl. It's also safer: The engine won't end up in your lap in a crash. Speaking of that engine, it's a turbocharged diesel. In racing, the better fuel economy of diesel means fewer pit stops, saving precious seconds. In the 908RC, it means 19.7 mpg-not bad for a 186mph screamer with four leather captain's chairs inside.