[chvtrkman]

Some interesting comments here about Dexcool vs. the green stuff. I always used Dexcool in our Suburban and never had any issues with sludge. However, around 2015 or 2016 it began "using" a small amount of coolant. I say using, because I was never able to detect any leaks, no puddle underneath when parked, nor any indication that a minor leak could be evaporating before dripping on floor. I thought maybe the expansion/overflow tank developed a crack but didn't see any leakage there either. I don't think we had a blown head gasket, it always ran great. To me it was just a mystery.. only had to add a quart or so once a month or so, depending on how much it was driven.