Audi S3 vs Mercedes-Benz CLS-Class: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Audi S3 burns about $2,800 of fuel annually against $2,900 for the Mercedes-Benz CLS-Class. That $100 yearly gap compounds to roughly $500 over five years and $800 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 Mercedes-Benz CLS-Class is the stronger commuter at 24 mpg city, while the Audi S3 pulls ahead on the interstate at 32 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 S3 is recorded with 3 distinct engine configurations (SIDI, SIDI; Mild Hybrid, SIDI;), the Mercedes-Benz CLS-Class with 2 (SIDI; Mild Hybrid, SIDI). Across 11 recorded Audi S3 configurations and 27 for the Mercedes-Benz CLS-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 S3 is offered with All-Wheel Drive, the Mercedes-Benz CLS-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 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 S3 emits 331 g/mile of CO2 versus 334 g/mile for the Mercedes-Benz CLS-Class. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.