Actually, bypassing the ignorance here, it can help.
True, cars are designed to run ~190f, and have thermostats to regulate them there. But, in hot weather (90f +) cars rise above the thermostat temp. So. If the car is running @ 210 w/o the additive, it will run cooler with it. This will equate to a small performance increase and better A/C performance. Red Line Water Wetter works by braking waters natural surface tension, making the water have more of a contact surface with the metal, pulling heat away faster. If you live in the south, a bottle or water wetter and 1/2 gal antifreeze (to lubricate water pump and stop corrosion) is the best mix.