Smooth, powerful, and efficient, both the four-cylinder in the 530i and the six-cylinder in the 540i motivate this big sedan with authority. The 540i's powertrain benefits from a little extra boost, care of a 48-volt hybrid system. Each engine pairs with an eight-speed automatic transmission that shifts intuitively and quickly, making the most of the available power. The 540i's six-cylinder is silky smooth and potent, and it makes delightful noises. Apart from the top-dog M5, which we review separately, the M550i is the athlete of the lineup, with a twin-turbocharged 4.4-liter V-8 under its hood. In our testing, the M550i sprinted through our acceleration runs quicker than the Audi S6 and Mercedes-AMG E53, hitting 60 mph in just 4.1 seconds. All 5-series models are competent handlers, but they lack the kind of driving verve we expect from BMW. Steering feedback is light, and the ride—even in the performance-oriented M550i—appears to be tuned more for comfort than driver involvement.