I have a 95 benz s320 and i put prestone antifreeze in there and i am planning on changing the antifreeze, because i heard it's not recommended to put other antifreeze in there, it makes the car run hot. I got 2 gallons of antifreeze from the dealer and i want to know what is the best way to flush the radiator and if i should put on gallon antifreeze and one gallon water, does it has to be tap water or distilled water?