Ron, both my Cats have the red extended life in them. Parts man at the Cat place is a very knowledgeable guy. He told me it won't hurt the cooling properties if I add green to the red but even a little of it will remove the long life properties of the high $$$ red stuff. It is also OK to add red to green stuff but you'll be wasting money because the red is more expensive and won't make the green more long lived.

Adding green to my Cats would be harmful because I removed the can with a rock inside that many folks call a "Filter". Would need to put that back on and start conditioning coolant if I contaminated the green stuff. MT, being newer, never had anything but green in it so it never had the can with a rock inside "Filter"