extended life coolant

[greydan]

I've put new hoses and a 3 core in my '87, and want to put extended life coolant in it. Have two other newer vehicles that use it, and would rather not have two kinds around.
I was cautioned by two people,
that I shouldn't put it in a car that had regular ethlyn glycol in it before. I called Havoline and they said no-problem. (what else would I expect them to say)
Anyone have any expereince with this? The reason I was given 'not to', was that it caused blown head gaskets ?????