1. BMW 3 Series / 4 Series - 77,921 units
And at the top of our list, and probably no surprise if you keep your eyes out on the road, is the BMW 3 Series. And since sales of the 4 Series has barely begun, we also decided to group the sales figures to make it a level playing field. Starting off its lineup is the 320i that has a base MSRP of $33,675. Under the hood is the German automaker’s 2.0-liter turbocharged four-cylinder engine with 180 hp and can get up to 36 mpg on the highway. What undoubtedly helps make the 3 Series so popular is the plethora of engine options available to buyers, ranging from the 240-hp 328i to the 300-hp 335i.