Silicone organic blends for use as lubricating oils, hydraulic fluids,
dielectric fluids, coolants, and in compressor or vacuum pump
applications, have improved viscosity stability when the polydispersity of
the silicone fluids used in these blends, i.e., their molecular weight
distribution (M.sub.w /M.sub.n), exceeds 1.5. The viscosity rise of the
silicone organic blend is less than one centistoke (mm.sup.2 /s) when aged
14 days in an oven at 100.degree. C., compared to viscosity rises of about
1.3 to over 3.5 centistokes (mm.sup.2 /s) for commercial silicone organic
blends using silicone fluids with polydispersity less than 1.5.