While other automakers are looking to replace displacement with forced-induction (turbos and super chargers) Infiniti stuck to its guns for the M56 S. It even increased the displacement of its top-of-the-line V8 from 4.5 liters to 5.6, helping it naturally produce 440 hp. That's 40 more than the BMW 550i and 58 more than the Mercedes-Benz E550. It's got power to burn, and you can feel it. There's no greater feeling that stomping on the accelerator and not having to wait for a turbine to spool up. With more power, however, comes less gas mileage. The M56 has an average fuel mileage of 20 mpg, and even if you switch the car into its "Eco" mode which plays with the accelerator and short-shifts the engine, you'll still find the car guzzling fuel. But, hey, we feel it's an even trade-off.