Name brand pure stuff and distilled water. I just make sure it says safe for aluminum on the back. Distilled water because you do not want the dissolved solids found in tap water. They can clog the radiator if there are enough minerals in the water. Mix to the ratio indicated on the rear for your temperatures. The water actually does most if not all of the cooling and the antifreeze lowers the freezing point as well as increasing the boiling point from 32/0 and 212/100 degrees to the different levels. So you may only need 40/60 or even less in mild climates. Water has a quite high specific heat which retains the heat of the engine block then dissipates it as it flows through the radiator. Running pure distilled water is fine but running pure coolant is a no no.