Kia K4 vs Mazda 3: Specs Compared

Running cost over five years: at the EPA's 15,000-mile-a-year assumption the Kia K4 burns about $1,800 of fuel annually against $1,850 for the Mazda 3. That $50 yearly gap compounds to roughly $250 over five years and $400 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 Mazda 3 leads in both cycles — 30 mpg city and 40 mpg highway against 30 and 40 mpg — so its fuel-efficiency advantage holds whether you commute in traffic or cover long highway miles.

Powertrain choice: the Kia K4 is recorded with 3 distinct engine configurations (SIDI, 2.0, with DMS), the Mazda 3 with 4 (SIDI, SIDI; With Cylinder Deactivation, SIDI; Without Cylinder Deactivation). Across 8 recorded Kia K4 configurations and 97 for the Mazda 3, 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 Kia K4 is offered with Front-Wheel Drive, the Mazda 3 with 4-Wheel Drive, Front-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 Midsize 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 Kia K4 emits 264 g/mile of CO2 versus 266 g/mile for the Mazda 3. Emissions track fuel consumption almost exactly, so the cleaner vehicle here is also the cheaper one to fuel.