Audi A8 vs Infiniti Q50: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Infiniti Q50 burns about $2,450 of fuel annually against $2,850 for the Audi A8. That $400 yearly gap compounds to roughly $2,000 over five years and $3,200 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 and highway economy: the Infiniti Q50 leads in both cycles — 29 mpg city and 36 mpg highway against 24 and 36 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the Audi A8 is recorded with 4 distinct engine configurations (SIDI; Mild Hybrid, SIDI; PHEV, SIDI), the Infiniti Q50 with 4 (SIDI, 3.5, 2.0). Across 28 recorded Audi A8 configurations and 60 for the Infiniti Q50, 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 A8 is offered with All-Wheel Drive, 4-Wheel Drive, the Infiniti Q50 with All-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 Large Cars and Midsize 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 A8 emits 213 g/mile of CO2 versus 286 g/mile for the Infiniti Q50. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.