Wondering why people complain that Yaris' cant get good mileage?!

[CtrlAltDefeat]

No, cold denser air helps mpg. For simplicity's sake lets say you need x amount of hp to maintain whatever speed. With hot air, the engine has to use less fuel per stroke, because the lower oxygen level but in order for the engine to output the proper hp and maintain the speed, the rpm has to go up. With the higher rpm being used to maintain the same speed, the hotter air gets worse mpg. Sure it uses micro-grams less fuel per stroke per cyl with the hot air, but every single additional rotation that it has to use to maintain hp uses an additional unit of fuel in each cyl...