What we have here are two Sedans from Infiniti with some differences, such as the horsepower and fuel economy. And finally, the 2015 Infiniti Q40 has a more powerful engine than the 2016 INFINITI Q50, and it gets 2.2 fewer miles on a gallon of fuel. Among similarities are the body structure, market segment, starting price, ground shadow size, height, and maximum occupancy.