Audi S4 vs Ford Mustang: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Ford Mustang burns about $2,350 of fuel annually against $3,150 for the Audi S4. That $800 yearly gap compounds to roughly $4,000 over five years and $6,400 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 Ford Mustang leads in both cycles — 22 mpg city and 33 mpg highway against 21 and 30 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the Audi S4 is recorded with 1 distinct engine configuration (SIDI), the Ford Mustang with 4 (5.2, 5.0, SIDI & PFI). Across 12 recorded Audi S4 configurations and 133 for the Ford Mustang, 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 S4 is offered with All-Wheel Drive, 4-Wheel Drive, the Ford Mustang with Rear-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 Subcompact 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 Ford Mustang emits 341 g/mile of CO2 versus 363 g/mile for the Audi S4. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.