Audi A3 vs Mercedes-Benz S-Class: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Audi A3 burns about $1,900 of fuel annually against $2,900 for the Mercedes-Benz S-Class. That $1,000 yearly gap compounds to roughly $5,000 over five years and $8,000 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 Audi A3 leads in both cycles — 37 mpg city and 41 mpg highway against 24 and 31 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the Audi A3 is recorded with 4 distinct engine configurations (SIDI, SIDI; Mild Hybrid, SIDI; PHEV), the Mercedes-Benz S-Class with 4 (SIDI; Mild Hybrid, 6.0, SIDI; PHEV). Across 36 recorded Audi A3 configurations and 106 for the Mercedes-Benz S-Class, 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 A3 is offered with All-Wheel Drive, Front-Wheel Drive, 4-Wheel Drive, the Mercedes-Benz S-Class with All-Wheel Drive, 4-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 Subcompact Cars and Large 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 Mercedes-Benz S-Class emits 106 g/mile of CO2 versus 138 g/mile for the Audi A3. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.