Anyone knows if it is OK to mix the green and the pink coolant?  Prestone
makes a phosphate free coolant that is pink and I have been topping off the
coolant tank with this kind of coolant.  Now my mechanic say that I should
not mix them but he does not know why.  The Prestone conatiner says that
the pink coolant is compatible with other coolants.  Anyone knows why they
should not be mixed?

Sorin