For 2021, the 2 top-end Mazda 3 models are powered by a SKYACTIV-G 2.5L turbo engine that delivers 227 horsepower at 5,000 rpm and 310 lb-ft of torque at 2,000 rpm on 87-octane fuel. With 93-octane gas, the power output shoots up to 250 horsepower and 320 lb-ft of torque, although peak torque arrives slightly…