2015 BMW Z4 Values & Cars for Sale | Kelley Blue Book

Our Expert Ratings come from hours of both driving and number crunching to make sure that you choose the best car for you. We comprehensively experience and analyze every new SUV, car, truck, or minivan for sale in the U.S. and compare it to its competitors. When all that dust settles, we have our ratings.

We require new ratings every time an all-new vehicle or a new generation of an existing vehicle comes out. Additionally, we reassess those ratings when a new-generation vehicle receives a mid-cycle refresh — basically, sprucing up a car in the middle of its product cycle (typically, around the 2-3 years mark) with a minor facelift, often with updates to features and technology.

Rather than pulling random numbers out of the air or off some meaningless checklist, KBB’s editors rank a vehicle to where it belongs in its class. Before any car earns its KBB rating, it must prove itself to be better (or worse) than the other cars it’s competing against as it tries to get you to spend your money buying or leasing.

Our editors drive and live with a given vehicle. We ask all the right questions about the interior, the exterior, the engine and powertrain, the ride and handling, the features, the comfort, and of course, about the price. Does it serve the purpose for which it was built? (Whether that purpose is commuting efficiently to and from work in the city, keeping your family safe, making you feel like you’ve made it to the top — or that you’re on your way — or making you feel like you’ve finally found just the right partner for your lifestyle.)

We take each vehicle we test through the mundane — parking, lane-changing, backing up, cargo space and loading — as well as the essential — acceleration, braking, handling, interior quiet and comfort, build quality, materials quality, reliability.