The thermal conductivity data shown here was measured by NIST using a transient hot-wire instrument at pressures ranging from 0.4 to 69 MPa across isotherms from 300 K to 500 K (27 °C to 227 °C). The values tabulated here correspond to the lowest-pressure measurements at each isotherm, which are representative of near-ambient conditions.

Thermal conductivity decreases approximately linearly with increasing temperature over this range, falling from about 0.145 W/(m·K) at 83 °F (28 °C) to about 0.114 W/(m·K) at 439 °F (226 °C). The combined expanded uncertainty in the thermal conductivity measurements is approximately ±1 %.

MIL-PRF-23699 is a fully qualified synthetic turbine engine oil based on polyol esters (POE), widely used in aircraft gas turbine engines. Its thermal conductivity is significantly lower than water and is relatively insensitive to pressure at modest pressures.