Audi A4 vs BMW 3 Series: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the BMW 3 Series burns about $2,200 of fuel annually against $2,450 for the Audi A4. That $250 yearly gap compounds to roughly $1,250 over five years and $2,000 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 and highway economy: the BMW 3 Series leads in both cycles — 31 mpg city and 43 mpg highway against 27 and 37 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the Audi A4 is recorded with 3 distinct engine configurations (SIDI; Mild Hybrid, SIDI, SIDI; FFV), the BMW 3 Series with 4 (SIDI & PFI; Mild Hybrid, SIDI, SIDI; PHEV). Across 35 recorded Audi A4 configurations and 105 for the BMW 3 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 3 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 BMW 3 Series emits 158 g/mile of CO2 versus 284 g/mile for the Audi A4. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.