Audi A4 vs BMW 4 Series: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Audi A4 burns about $2,450 of fuel annually against $2,450 for the BMW 4 Series. That $0 yearly gap compounds to roughly $0 over five years and $0 over eight — often more than the price difference between two trims of the same vehicle, and the single largest running-cost line item separating these two.

City versus highway split: the BMW 4 Series is the stronger commuter at 28 mpg city, while the Audi A4 pulls ahead on the interstate at 37 mpg highway. If most of your driving is stop-and-go traffic the city figure is the one to weigh; for long-distance highway mileage the reverse is true, and the two vehicles effectively swap places depending on how you drive.

Powertrain choice: the Audi A4 is recorded with 3 distinct engine configurations (SIDI; Mild Hybrid, SIDI, SIDI; FFV), the BMW 4 Series with 4 (SIDI & PFI; Mild Hybrid, SIDI, SIDI; Mild Hybrid). Across 35 recorded Audi A4 configurations and 160 for the BMW 4 Series, the wider the engine spread the more the real-world fuel efficiency depends on which version you actually buy, so check the specific model year and drivetrain rather than the headline number.

Drivetrain and class: the Audi A4 is offered with All-Wheel Drive, Front-Wheel Drive, the BMW 4 Series with Rear-Wheel Drive, All-Wheel Drive. All-wheel drive typically costs one to two mpg combined against the same vehicle in front- or rear-wheel drive, which is worth remembering when the gap between these two is small. The EPA classes them as Compact Cars and Compact Cars respectively — the class drives the interior volume, cargo space and passenger space each one is measured against.

Tailpipe emissions: at their cleanest configurations the Audi A4 emits 284 g/mile of CO2 versus 285 g/mile for the BMW 4 Series. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.