I think the RV antifreeze is propylene glycol and regular antifreeze is ethylene glycol. I think the propylene is supposed to be less toxic. It has slightly different properties than ethylene but I don't remember exactly what. Seems to me it may have been slightly denser and therefore a better heat exchanger. When I worked for Esso we sold quite a bit to the oil patch for their heat exchangers at natural gas compressor stations.I use distilled water and RV antifreeze. I'm not sure what the difference is with regular antifreeze and the RV version but I read sometime ago that it is better for the closed loop spindle cooling. I also have a piece of Silver in the cooling reservoir for antimicrobial purposes.