Abstract: A heat transfer fluid composition comprising a polyalkylene glycol initiated by a hydric initiator having a functionality of at least 1 and extended with ethylene oxide, wherein the polyalkylene glycol comprises at least 30 percent by weight ethylene oxide and having a volumetric heat capacity at 100° C. of at least 2.0 J/cm3-K; and an additive package which comprises an acid scavenger, wherein the acid scavenger is an aspartic acid, aspartic acid amide, a Group V aspartic acid salt, their derivatives, or a combination thereof is provided. Also provided are such fluids which meet the bio-no-tox criteria of European Community directive EC/1999/45 (as amended by EC/2006/8). Further provided are monofluid-type engine lubricating and cooling fluids comprising such heat transfer fluid.