Thermal diffusivity (α) describes how quickly a material conducts heat relative to its ability to store thermal energy. It is computed from three independently measured properties: α = λ / (ρ · c_p), where λ is thermal conductivity [W/(m·K)], ρ is density [kg/m³], and c_p is isobaric specific heat capacity [J/(kg·K)].

The data range here is limited to 83–158 °F (28–70 °C) where all three source datasets overlap: density was measured over 5–70 °C (Table 23), specific heat capacity over 0–219 °C (Table 14), and thermal conductivity from approximately 28–226 °C (Table A4). The thermal conductivity is linearly interpolated at each temperature step.

MIL-PRF-23699 has a thermal diffusivity of roughly 8.1×10⁻⁸ m²/s near room temperature, decreasing slightly with temperature. This is an order of magnitude lower than water (~1.4×10⁻⁷ m²/s), consistent with its role as a thermal barrier lubricant rather than a coolant.