Audi S4 vs Lexus IS: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Lexus IS burns about $2,900 of fuel annually against $3,150 for the Audi S4. 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 Lexus IS leads in both cycles — 22 mpg city and 32 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 Lexus IS with 2 (SIDI & PFI, SIDI). Across 12 recorded Audi S4 configurations and 52 for the Lexus IS, 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 Lexus IS with All-Wheel Drive, 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 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 Lexus IS emits 345 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.