I personally use Prestone coolant with distilled water. I don´t use the orange dex cool because in my opinion it sucks. drain it out cold then fill up with water and a bottle of Prestone Super flush. start the car with the radiator cap off and let it warm up unitl the thermostat opens. add water as needed to fill it up. put the cap on (quickly!) and drive around for a while. No you will not hurt anything. Water actually transfers heat faster than antifreeze and no corrosion is going to happen. shut it off and let it cool down. drain everything and then fill ´er up with distilled water and Prestone Antifreeze. repeat yearly.