Thermal diffusivity (α) describes how quickly a fluid conducts heat relative to its ability to store thermal energy. It is computed from three independently published 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)].

This page reuses the exact same extrapolated specific heat, thermal conductivity, and density datasets built for the Prandtl Number page, so its usable range is −40 °F to 300 °F for all four grades — wider than the Prandtl page because α does not depend on kinematic viscosity, which was the tightest constraint there. Skydrol PE-5 is included here (unlike the thermal expansion page) because α only needs a density value at each temperature, not a density slope — PE-5's constant 25 °C density is usable for that, just less accurate than a real curve.

Skydrol's thermal diffusivity is on the same order of magnitude as other aviation hydraulic fluids and lubricants (roughly 10⁻⁸–10⁻⁷ m²/s), an order of magnitude lower than water, consistent with its role as a working fluid rather than a coolant.