The redesign of Buick's flagship rests on a new structure that resulted in a weight reduction of 300 pounds and improved visibility. Buick stretched the wheelbase by three inches, resulting in more passenger space, while keeping the footprint the same. Under the hood, a revised 3.6-liter V6 is mated to an eight-speed automatic, forming a smooth powertrain. Handling is sound and the cabin is quiet. The ride on the optional 20-inch tires has trouble coping with some harshness. We think the standard 18-inch tires are a better choice. Inside, there's an 8-inch touchscreen, fewer buttons, and Apple CarPlay and Android Auto capability, but the unintuitive gear selector is maddening. Advanced electronic safety features and all-wheel drive are available.