Mercedes-Benz SL-Class vs Porsche 718: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Porsche 718 burns about $3,150 of fuel annually against $3,300 for the Mercedes-Benz SL-Class. That $150 yearly gap compounds to roughly $750 over five years and $1,200 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 Porsche 718 is the stronger commuter at 21 mpg city, while the Mercedes-Benz SL-Class pulls ahead on the interstate at 28 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 Mercedes-Benz SL-Class is recorded with 4 distinct engine configurations (SIDI, SIDI; Mild Hybrid, SIDI; PHEV), the Porsche 718 with 1 (SIDI). Across 40 recorded Mercedes-Benz SL-Class configurations and 91 for the Porsche 718, 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 Mercedes-Benz SL-Class is offered with All-Wheel Drive, Rear-Wheel Drive, the Porsche 718 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 Two Seaters and Two Seaters respectively — the class drives the interior volume, cargo space and passenger space each one is measured against.

Tailpipe emissions: at their cleanest configurations the Porsche 718 emits 375 g/mile of CO2 versus 379 g/mile for the Mercedes-Benz SL-Class. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.