I was wondering if that low-tox/enviro-friendly coolant works just as well as regular Prestone coolant. Anyone use this stuff or know if the thermal properties are the same? I only ask because I have a crap load of it that I found in the shed (previous owner left it behind).

 

I've used Sierra (low-tox) antifreeze in many of my cars. Sierra is Propylene glycol-based rather than Ethylene glycol-based (Prestone, Peak, etc.) While I'm no chemical engineer and can't speak for the specific cooling properties of either one, I will say that I've never noticed a difference between the two. Sierra works just as well, as far as my temp. gauge can tell, and seems to protect just as well with regard to corrosion.