A gasoline engine transform approximately 34 percent of the fuel's chemical energy into mechanical energy. if energy is conserved what happenes to the other 66 percent?

Only 34 percent of the fuel's chemical energy into mechanical energy. the remaining 66 percent is part of the heat produced from burning a fuel may become rejected waste heat, overcoming frictional forces when gears are moving, it can also decimated as sound energy produced by the engine.