best antifreeze for old cars

You should never mix different types of coolant. Ok if it is same formula but no cross mixing.
Well thats great accept you've just told everyone that has any aluminum parts in their engines they should running HOAT when chances are they've been running OAT & unless you pull the block drains which virtually no one does there will still be about a gallon of coolant in most engines....

All these wonderful new technologies that don't mix with the real world stuff is BS