Mercedes-Benz GLB-Class vs Porsche Cayenne: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Mercedes-Benz GLB-Class burns about $2,700 of fuel annually against $3,300 for the Porsche Cayenne. That $600 yearly gap compounds to roughly $3,000 over five years and $4,800 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 and highway economy: the Mercedes-Benz GLB-Class leads in both cycles — 25 mpg city and 33 mpg highway against 21 and 29 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the Mercedes-Benz GLB-Class is recorded with 2 distinct engine configurations (SIDI; Mild Hybrid, SIDI), the Porsche Cayenne with 4 (SIDI, SIDI; PHEV, 4.0). Across 20 recorded Mercedes-Benz GLB-Class configurations and 97 for the Porsche Cayenne, 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 GLB-Class is offered with Front-Wheel Drive, All-Wheel Drive, 4-Wheel Drive, the Porsche Cayenne with All-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 Small Sport Utility Vehicle 4WD and Standard Sport Utility Vehicle 4WD 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 Cayenne emits 174 g/mile of CO2 versus 311 g/mile for the Mercedes-Benz GLB-Class. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.