MIL-PRF-5606 Specific Heat Capacity Chart

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Measured values for MIL-PRF-5606: -18 °C to 204 °C (-0.4 °F to 399.2 °F) at ambient pressure, at five temperatures.
The line is a straight-line fit to those five measurements and is drawn only across that range; nothing is extrapolated.

Markers are the five NADC-79248-60 measured points. The blue MIL-PRF-23699 series is shown for comparison over its own measured range, 0 °C to 219 °C.

Data from: NADC-79248-60 (Conte & Hammond, 1980), DTIC ADA081597, Table 7 (measured); MIL-PRF-23699 data from NIST IR 8263, Table 14.

Toggle data sets by clicking the legend.

MIL-PRF-5606 Specific Heat Capacity Calculator
Degrees (°F):
Degrees (°C):
J / (kg·K):  
kJ / (kg·K):  
J / (g·K):  
kWh / (kg·K):  
Btu / (lbm·°F):  
cal / (g·°C):  
MIL-PRF-23699 (J/(kg·K)):  

Calculator valid -18 °C to 204 °C (-0.4 °F to 399.2 °F), ambient pressure, using the linear fit to the NADC measurements. The MIL-PRF-23699 row is shown only within that fluid's 0–219 °C measured range.

Specific Heat Capacity of MIL-PRF-5606
What Is Isobaric Specific Heat Capacity (Cp)?

Specific heat capacity (Cp) is the amount of heat required to raise the temperature of a unit mass by one degree at constant pressure. For MIL-PRF-5606 it is measured in J/(kg·K) [SI] or Btu/(lbm·°F) [Imperial], and governs sizing of heat exchangers and thermal management systems. The heat transfer equation is:

\[ Q = \dot m\,C_p\,\Delta T \]

where Q is heat flow (W or BTU/hr), ṁ is mass flow rate, and ΔT is the temperature difference across the heat exchanger or system boundary.

About This Data

The specific heat values are the MIL-H-5606 entries of Table 7 in NADC-79248-60 (Conte & Hammond, Naval Air Development Center, 1980, DTIC ADA081597), tabulated at -18, 38, 93, 149 and 204 °C. The report does not state the measurement method, the specification revision (MIL-H-5606 predates the MIL-PRF designation) or the lot tested, and it gives no uncertainty.

The smooth curve is the straight-line fit cp = 1786.96 + 4.3331 · T°C J/(kg·K), used only between -18 °C and 204 °C. It departs from the five measured values by at most 7.6 J/(kg·K). Cp rises nearly linearly with temperature, from 1714 J/(kg·K) at -18 °C to 2676 J/(kg·K) at 204 °C.

MIL-PRF-5606 — Isobaric Specific Heat Capacity vs. Temperature
Temp (°C) Temp (°F) Measured Cp (J/(kg·K)) Measured Cp (Btu/(lbm·°F)) Linear fit (J/(kg·K))
-18-0.417140.4101709.0
38100.419440.4651951.6
93199.421950.5252189.9
149300.224250.5802432.6
204399.226760.6402670.9

Measured columns are NADC-79248-60 Table 7 (MIL-H-5606). Btu/(lbm·°F) values are as printed in the report at 0, 100, 200, 300 and 400 °F. Linear fit: cp = 1786.96 + 4.3331 · T°C J/(kg·K), -18 to 204 °C only. No uncertainty is given in the report.

MIL-PRF-5606 vs MIL-PRF-23699

MIL-PRF-5606 is a petroleum (mineral oil) hydraulic fluid; MIL-PRF-23699 is a polyol-ester turbine engine oil. Over 0–204 °C, where both have data, MIL-PRF-5606 has the higher specific heat. The difference grows from about 50 J/(kg·K) (3 %) at 0 °C to about 370 J/(kg·K) (16 %) at 204 °C.

Temp (°C) Temp (°F) MIL-PRF-5606 (J/(kg·K)) MIL-PRF-23699 (J/(kg·K)) Difference (J/(kg·K)) Difference (% of 23699)
-18-0.41709.0———
032.01787.01737.050.02.9 %
2068.01873.61785.088.65.0 %
38100.41951.61835.0116.66.4 %
50122.02003.61868.0135.67.3 %
70158.02090.31924.0166.38.6 %
93199.42189.91990.0199.910.0 %
100212.02220.32010.0210.310.5 %
149300.22432.62150.0282.613.1 %
200392.02653.62291.0362.615.8 %
204399.22670.92302.0368.916.0 %
210410.0—2318.0——
219426.2—2343.0——

MIL-PRF-5606 values use the linear fit to the NADC-79248-60 measurements, -18–204 °C only. MIL-PRF-23699 values are linearly interpolated from NIST IR 8263 Table 14, 0–219 °C only. "—" means the fluid has no measurement at that temperature (extrapolated values are deliberately not used). The two datasets come from different sources, labs and pressures, so small differences should not be over-interpreted.

Sources
  • A. A. Conte Jr. and J. L. Hammond, Development of a High Temperature Silicone Base Fire-Resistant Hydraulic Fluid, NADC-79248-60, Naval Air Development Center, Warminster PA, 5 Feb 1980. DTIC ADA081597. apps.dtic.mil/sti/tr/pdf/ADA081597.pdf. Table 7 (MIL-H-5606 column), accessed 12 Oct 2026.
  • US Department of Defense, MIL-PRF-5606H, Performance Specification: Hydraulic Fluid, Petroleum Base; Aircraft, Missile, and Ordnance, 7 June 2002. everyspec.com. Identification of the fluid.
  • Bruno et al., Thermophysical Properties of Polyol Ester Lubricants, NIST IR 8263, 2019. doi.org/10.6028/NIST.IR.8263. MIL-PRF-23699 comparison data (Table 14).

The NADC report does not state the specification revision or lot of the MIL-H-5606 tested, the measurement method, or any measurement uncertainty.

Cite This Work