KasperCalc: MIL-PRF-5606 Thermal Expansion Coefficient

MIL-PRF-5606 Volumetric Thermal Expansion Coefficient (β)

β = −(1/ρ)(dρ/dT), derived from the straight-line fit to the four NADC-79248-60 Table 2 atmospheric densities. The curve is drawn only from 38 °C to 204 °C (100.4–399.2 °F); nothing is extrapolated.

Circles are the four tabulated β values at 38, 93, 149 and 204 °C. The dotted line is the NADC report's own average cubical expansion, 8.6 × 10⁻⁴ /°C over 38–149 °C, shown as a cross-check only. Dashed blue lines represent linearly extrapolated MIL-PRF-23699 data beyond its 41–158 °F measured range (NIST IR 8263 data range limit).

Toggle data sets by clicking the legend.

MIL-PRF-5606 Percent Volume Change Relative to 100.4 °F (38 °C)

ΔV/V₀ = (ρ₀ − ρ) / ρ × 100%, referenced to 100.4 °F (38 °C) where ρ₀ = 842.42 kg/m³ from the same density fit. Negative values mean the oil is denser (contracted) relative to 38 °C.

The reference is 100.4 °F (38 °C), not the 68 °F (20 °C) used on the MIL-PRF-23699 page, because 38 °C is the lowest temperature with a measured MIL-PRF-5606 density; nothing is extrapolated below it.

Valid 38–204 °C (100.4–399.2 °F) only. Circles are the four tabulated temperatures.

Toggle data sets by clicking the legend.

MIL-PRF-5606 Thermal Expansion Calculator

Degrees (°F):

Degrees (°C):

β × 10⁻⁴ (1/K):

β × 10⁻⁵ (1/K):

β × 10⁻⁶ (ppm/K):

β (1/K):

β (1/°R):

Density, linear fit (kg/m³):

% Vol. Change from 100.4°F:

MIL-PRF-23699 β × 10⁻⁴ (1/K):

Calculator valid 100.4 °F to 399.2 °F (38 °C to 204 °C) only, using the derived fit to the NADC-79248-60 atmospheric densities. Outside that range the result is "Out of Range". The MIL-PRF-23699 row is shown only within that fluid's 41–158 °F measured range.

Thermal Expansion of MIL-PRF-5606 Petroleum Hydraulic Fluid

Volumetric Thermal Expansion Coefficient — β (derived)

The volumetric thermal expansion coefficient β describes how much a fluid expands per degree of temperature rise at constant pressure:

\[ \beta = -\frac{1}{\rho}\,\frac{d\rho}{dT} \]

NADC-79248-60 does not tabulate β for MIL-H-5606. β is therefore derived from its atmospheric density data. The four Table 2 densities are fitted with a least-squares straight line, ρ = 869.517 − 0.71295 · T_°C kg/m³, and because the fit is linear the derivative is constant, giving

\[ \beta(T) = \frac{0.71295}{869.517 - 0.71295\,T_{\text{°C}}}\ \text{1/K} \]

β rises slowly with temperature as density falls: about 8.463 × 10⁻⁴ 1/K at 38 °C (100 °F) and about 9.846 × 10⁻⁴ 1/K at 204 °C (399 °F). The curve is valid only between those two temperatures, the range of the measured densities.

Cross-Check Against the Report's Average

NADC-79248-60 (p.15) gives a single average cubical expansion coefficient of 8.6 × 10⁻⁴ /°C over 38–149 °C (100–300 °F), with no point values. The average of the derived β over the same interval is 8.887 × 10⁻⁴ /°C, about 3 % higher. The report does not state how its average was computed, so the difference is shown and not resolved.

Data Source and Range

The density fit is built from the MIL-H-5606 atmospheric column of Table 2 in NADC-79248-60, at 38, 93, 149 and 204 °C (100, 200, 300 and 400 °F). The report's Table 9 covers Nadraul MS-6 rather than MIL-H-5606. No density or expansion data below 38 °C were found in the sources used, so the chart and calculator are not extended below 100.4 °F. Nothing is extrapolated above 399.2 °F either. The report gives no uncertainty for its measurements, and the measured lot and specification revision are not stated.

MIL-PRF-5606 — Thermal Expansion vs. Temperature

Temp (°C)	Temp (°F)	Density, linear fit (kg/m³)	β × 10⁻⁴ (1/K)	ΔV/V₀ (%) vs 38 °C	Notes
38	100.4	842.4	8.463	0.000	Tabulated (NADC Table 2, derived)
50	122.0	833.9	8.550	1.026	Fit
60	140.0	826.7	8.624	1.897	Fit
70	158.0	819.6	8.699	2.784	Fit
93	199.4	803.2	8.876	4.882	Tabulated (NADC Table 2, derived)
100	212.0	798.2	8.932	5.538	Fit
125	257.0	780.4	9.136	7.948	Fit
149	300.2	763.3	9.341	10.368	Tabulated (NADC Table 2, derived)
175	347.0	744.8	9.573	13.115	Fit
204	399.2	724.1	9.846	16.345	Tabulated (NADC Table 2, derived)

β = −(1/ρ)(dρ/dT) with ρ = 869.517 − 0.71295 T_°C kg/m³ (straight-line fit to the NADC-79248-60 Table 2 atmospheric densities), valid 38–204 °C only. Tabulated rows are the four β values from the derived data set.

Cross-Check: NADC Average vs. Derived Average

Quantity	Range (°C)	β × 10⁻⁴ (1/K)	Basis
NADC-79248-60 average cubical expansion	38–149	8.6	Report text, p.15 (no method stated)
Mean of derived β over the same range	38–149	8.887	Computed from the density fit

The derived mean is the average of β over the interval, equal to (1/ΔT)·ln(ρ₃₈/ρ₁₄₉) from the same fit. The two values differ by about 3 %.

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 the 38–70 °C band where both have data, MIL-PRF-5606 has the higher β, by about 0.76–0.80 × 10⁻⁴ 1/K (about 10 %). Both density slopes are similar (−0.713 and −0.754 kg·m⁻³·K⁻¹), but MIL-PRF-5606 is less dense (about 842 against 977 kg/m³ at 38–40 °C), so the same slope gives a larger β.

Temp (°C)	Temp (°F)	MIL-PRF-5606 β × 10⁻⁴ (1/K)	MIL-PRF-23699 β × 10⁻⁴ (1/K)	Difference (× 10⁻⁴ 1/K)	Difference (% of 23699)
38	100.4	8.463	7.705	0.758	9.8 %
40	104.0	8.477	7.717	0.760	9.9 %
45	113.0	8.514	7.747	0.766	9.9 %
50	122.0	8.550	7.777	0.773	9.9 %
55	131.0	8.587	7.808	0.779	10.0 %
60	140.0	8.624	7.838	0.785	10.0 %
65	149.0	8.661	7.869	0.792	10.1 %
70	158.0	8.699	7.900	0.799	10.1 %
93	199.4	8.876	—	—	—
149	300.2	9.341	—	—	—
204	399.2	9.846	—	—	—

MIL-PRF-5606 values use the derived fit to the NADC-79248-60 atmospheric densities, 38–204 °C only. MIL-PRF-23699 values are interpolated from NIST IR 8263 Table 23 (density, with the same constant slope used on the MIL-PRF-23699 page), 5–70 °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 (NIST ~83 kPa; NADC atmospheric), 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 2 (MIL-H-5606 columns) and p.15 (average cubical expansion), 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; no finished-fluid density limit.
NYCO, Hydraunycoil FH 51 Technical Data Sheet (TDS_FH51-1E11), 2020. aircraftspruce.com/catalog/pdf/FH51TDS.pdf. Typical density.
ExxonMobil, Mobil Aero HF Series product page. mobil.com. Typical specific gravity; HF vs HFA column assignment unverified.
Chevron, Hydraulic Oil 5606 Product Data Sheet, Jan 2024. Chevron PDS. Typical density (general-purpose industrial/marine oil that claims to meet MIL-PRF-5606H).
LANXESS, ROYCO 756/756A Data Sheet, effective 6 Jan 2017. ROYCO 756 data sheet. Typical density in lb/gal.
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 23).

The NADC report does not state the specification revision or lot of the MIL-H-5606 tested, and gives no measurement uncertainty. Manufacturer values are single-lot typicals; none of them gives thermal expansion data, and none is used on this page.

MIL-PRF-5606 Petroleum Hydraulic Fluid Thermal Expansion Coefficient Calculator

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