What happens when you put ethanol in your car instead of gas?

Assuming you are asking about putting E85 ( 85% ethanol and 15% gas ) into a regular gas burning vehicle your engine would run rough or not at all and you would cause corrosion to your normal rubber fuel lines and fuel pump. To properly convert a gas burning car to one that burns E85 one must replace the rubber fuel lines and fuel pump with ones made for flex fuel vehicles and buy an aftermarket ignition control unit that changes the opening of your injectors as compared with the engine timing.