Abstract: Heat transfer fluids which can be used over a broad range of temperatures such as from ?125° C. to +175° C. are disclosed. These transfer fluids consist essentially of a mixture of two either narrowly defined structurally non-identical alkyl- or polyalkyl-benzene components or a mixture of a narrowly defined aromatic alkyl- or polyalkyl-benzene component and an aliphatic hydrocarbons component. The level of the various ingredients is such that the transfer fluids exhibit a cloud point below ?100° C., a vapor pressure at +175° C. below 827 kPa and a viscosity, measured at the cloud point temperature +10° C., below 400 cP.

Abstract: Heat transfer fluids which can be used over a broad range of temperatures such as from 175° C. to ?145° C. are disclosed. The heat transfer fluids consist essentially of a mixture of at least two structurally non-identical cycloalkane-alkyl or -polyalkyl compounds, or a mixture of at least two structurally non-identical aliphatic hydrocarbons, or a mixture of a cycloalkane-alkyl or -polyalkyl compound and an aliphatic hydrocarbon. The individual components are present at levels such as to confer to the fluid composition a cloud point below ?100° C., a vapor pressure at +175° C. below 1300 kPa, and a viscosity, measured at the cloud point temperature +10° C., below 400 cP.