Joe! I agree with you, but the reson I said 3 is, because 90% of the time that is what they use here, and unless he switches all and blows out all lines and reservers, that is why I said 3, yes 4 is better but just have to make sure, no drop is left, otherwise he messes up his sytem. But then again ..... I messed up my system ones, and hope noone has to experience what I had to pay.