Kia Optima (2017) is 275 mm (10.83 inch) longer, 64 mm (2.52 inch) wider, 15 mm (0.59 inch) higher and has 91 liters (3.21 ft3) bigger cargo space than Mazda 3 (Sedan) (2016).
Mazda 3 (Sedan) (2016) is 245 kg (540 lbs) lighter than Kia Optima (2017).
