One last-un, Haro..
I thought that the Prestone Long-Life DEX compatible antifreeze was the gem, not the green stuff. I'm assuming that the green stuff is ethylene-glycol-based, and I know that mixing that with the G11 and G12 (even mixing the G11 with the G12) that I used to put in my Volkswagens was sudden sludgey death! Even the EG is acidic - though fortunately not as nasty as the Dex. Or is it that I just need to flush the gosh-darned heck out of the cooling system before I throw anything back in?
Also, if I come upon a blocked up coolant passage, should I try to unblock it? I'd think it would be the smart thing to do..