BMW Z4 vs Porsche 718: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the BMW Z4 burns about $2,700 of fuel annually against $3,150 for the Porsche 718. That $450 yearly gap compounds to roughly $2,250 over five years and $3,600 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 BMW Z4 leads in both cycles — 25 mpg city and 33 mpg highway against 21 and 27 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the BMW Z4 is recorded with 1 distinct engine configuration (SIDI), the Porsche 718 with 1 (SIDI). Across 25 recorded BMW Z4 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 BMW Z4 is offered with 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 BMW Z4 emits 312 g/mile of CO2 versus 375 g/mile for the Porsche 718. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.