The 4-Series doesn't have practicality on its to-do list. That means the back seat is a low priority, and you won't want to be in it if you're in your second decade on the planet or in anything beyond a size medium. If you're lucky and are riding up front--or driving--it's an entirely different story.
The 4-Series shares some engines and transmissions with the 3-Series, even has an identical 110.6-inch wheelbase as well as 182.5-inch overall length. It's lower by about two inches, and sits about a half-inch wider than its sedan kin.
The driver seat is low in the 4er, the steering wheel the size of an SUV's rudder. The base front seats have great comfort and support. We'd approve them for hours of use, but they don't have as many adjustments or the very firm bolstering of the excellent sport seats offered on the M Sport package. Those seats grip in all the right places for the kind of sporty driving the 4-Series encourages; heating and ventilation are a part of the deal.
Back-seat space suffers in the 4-Series because of its design. It sits three inches wider in all across the rear end versus the 3-Series, but the roofline drops quickly, and even long doors don't make it easy to get in back. It's a tough vehicle to justify if you carry three passengers often, but on short trips small adults won't have too much to complain over.
The bright spot: trunk space nearly matches that of a mid-size four-door, and in-car storage counts real cupholders, door-panel bottle holders, and a sizable glove box.
BMW fits a pretty spartan cabin in base 4-Series cars. They're dark and drab, and don't flatter the sweeping design. It's worth spending for some of the superior finishes on the options list, alluring combos of wood and metal and contrast-stitched leather.
BMW's big, beautiful dash-top screen displays crisp output from iDrive, but it's stuck on the dash like an afterthought.