KasperCalc: MIL-PRF-5606 Dynamic and Kinematic Viscosity

MIL-PRF-5606 Kinematic Viscosity Chart

Measured values for MIL-H-5606 at atmospheric pressure, six points from −54 °C to 204 °C (−65.2 °F to 399.2 °F); the 20.7 MPaG (3000 psig) and 55.2 MPaG (8000 psig) rows are markers only. Y-axis is logarithmic.

The atmospheric curve is a piecewise ASTM D341 interpolation through the six measured points, drawn only from −54 °C to 204 °C; nothing is extrapolated. There is no measurement between −40 °C and 38 °C, so the curve in that span is interpolation only.

Triangles are single-lot manufacturer typical values (not measurements). Crosses are the limits of MIL-PRF-5606H Table II (maximum at −54 and −40 °C, minimum at 40 and 100 °C), not measurements. The blue MIL-PRF-23699 curve is derived (ν = μ/ρ) from NIST IR 8263 dynamic viscosity and density, 16.89–126.85 °C only, and is dashed above 70 °C where its density is extrapolated; blue crosses and triangles are the MIL-PRF-23699G specification limits and typical values at −40, 40 and 100 °C.

Data from: NADC-79248-60 (Conte & Hammond, 1980), DTIC ADA081597, Table 1 (measured); MIL-PRF-5606H Table II (limits); MIL-PRF-23699 comparison from NIST IR 8263 Table B4 (dynamic viscosity), Table 23 (density) and the MIL-PRF-23699G property table on MIL-PRF-23699 General Properties.

Toggle data sets by clicking the legend.

MIL-PRF-5606 Dynamic (Absolute) Viscosity Chart

Computed from kinematic viscosity × density (μ = ν × ρ). Toggle data sets by clicking the legend. Y-axis is logarithmic.

Density source: straight-line fit to NADC-79248-60 Table 2 (atmospheric), valid only from 38 °C to 204 °C (100.4 °F to 399.2 °F). Dynamic viscosity is only computed within that range; no density was found below 38 °C. Circles are the four tabulated points (measured ν × measured ρ at the same temperature).

The blue MIL-PRF-23699 series is the NIST IR 8263 Table B4 dynamic viscosity of that fluid (generic to the specification), 16.89–126.85 °C only, with circles at the tabulated points.

MIL-PRF-5606 Viscosity Calculator

Degrees (°F):

Degrees (°C):

Kinematic Viscosity

mm²/s (= cSt):

Centistokes (cSt):

Stokes (cm²/s):

m²/s:

in²/s:

ft²/s:

Dynamic (Absolute) Viscosity

mPa·s (= cP):

Centipoise (cP):

Poise (g/(cm·s)):

Pa·s (Poiseuille):

lbm/(ft·s):

kg/(m·h):

MIL-PRF-23699 (comparison)

Kinematic, derived (cSt):

Dynamic (mPa·s):

Kinematic viscosity is valid −54 °C to 204 °C (−65.2 °F to 399.2 °F), atmospheric pressure, from the piecewise ASTM D341 interpolation; between −40 °C and 38 °C it is interpolation only. Dynamic viscosity is shown only from 38 °C to 204 °C, where a density fit exists. The MIL-PRF-23699 rows come from NIST IR 8263 Table B4 and are shown only within 16.89–126.85 °C; its kinematic value is derived as μ/ρ.

Viscosity of MIL-PRF-5606 Petroleum Hydraulic Fluid

About This Data

The kinematic viscosity values are the MIL-H-5606 columns of Table 1 in NADC-79248-60 (Conte & Hammond, Naval Air Development Center, 1980, DTIC ADA081597): atmospheric pressure at −54, −40, 38, 93, 149 and 204 °C, and 20.7 and 55.2 MPaG at 38, 93 and 149 °C. The report does not state the specification revision (MIL-H-5606 predates the MIL-PRF designation) or the lot tested, and it gives no uncertainty.

The smooth curve is a piecewise ASTM D341 interpolation: between neighbouring measured points it is a straight line in Y = log₁₀(log₁₀(ν + 0.7)) against X = log₁₀(T_°C + 273.15), with ν in cSt, and it passes exactly through every measured point. A single D341 line through all six points was not used because it misfits the data by −25 % at −54 °C and +19 % at 38 °C (the fluid contains a polymeric viscosity-index improver). The span from −40 °C to 38 °C has no measurement inside it, so values there are interpolation only. Nothing is extrapolated outside −54 °C to 204 °C.

No dynamic viscosity is tabulated in any source used. It is derived as μ = ν × ρ, and only where the density fit (ρ = 869.517 − 0.71295 · T_°C kg/m³, NADC Table 2 atmospheric) is valid, 38 °C to 204 °C. See also Density of MIL-PRF-5606.

MIL-PRF-5606 is a petroleum-based (mineral oil) aircraft hydraulic fluid, dyed red. The triangles on the chart are single-lot “typical” values taken from manufacturer data sheets for products sold against the specification; they are not measurements made for this site and carry no stated uncertainty.

Dynamic (Absolute) vs. Kinematic Viscosity

Dynamic (Absolute) Viscosity — μ

Dynamic viscosity measures a fluid's resistance to shear — the internal force per unit area required to make one layer slide past another. It is independent of density. The SI unit is the pascal-second (Pa·s); the common engineering unit is the millipascal-second (mPa·s), numerically equal to centipoise (cP).

\[ \tau = \mu\,\frac{du}{dy} \]

Kinematic Viscosity — ν

Kinematic viscosity is the ratio of dynamic viscosity to fluid density. The SI unit is m²/s; the common unit is mm²/s, numerically equal to centistokes (cSt). Hydraulic fluid specifications grade viscosity kinematically because viscometers measure time-of-flow under gravity, which naturally yields kinematic viscosity.

\[ \nu = \frac{\mu}{\rho} \quad\Rightarrow\quad \mu\ [\text{mPa}\cdot\text{s}] = \frac{\nu\ [\text{mm}^2/\text{s}] \times \rho\ [\text{kg/m}^3]}{1000} \]

MIL-PRF-5606 — Measured Viscosity

Temp (°C)	Temp (°F)	Kinematic, atm. (mm²/s)	20.7 MPaG (mm²/s)	55.2 MPaG (mm²/s)	Density, atm. (kg/m³)	Dynamic, atm. (mPa·s)

Kinematic columns are NADC-79248-60 Table 1 (MIL-H-5606). Density is NADC Table 2 and dynamic viscosity is the product of the two at the same temperature (derived, not tabulated in any source). “—” means no value at that temperature. Measured lot and specification revision are not stated in the report and no uncertainty is given.

Specification Limits (MIL-PRF-5606H Table II)

Temp (°C)	Temp (°F)	Kinematic viscosity limit (mm²/s)	Interpolated curve (mm²/s)

These are acceptance limits for the fluid, not measurements. The last column is the NADC-based curve on this page at the same temperature, for reference only (different lot, different era, no uncertainty stated).

Manufacturer Typical Values (not measurements)

Source	Temp (°C)	Temp (°F)	Kinematic viscosity (mm²/s)

Single-lot typical values, no uncertainty stated. The Mobil Aero HF values are read from a page-text extraction and the HF versus HFA column assignment is unverified. The Chemsol sheet has garbled temperature labels (numbers copied as printed) and should be used with low confidence. The Chevron oil is a general-purpose industrial/marine oil that claims to meet MIL-PRF-5606H, and its viscosity differs from the aviation-grade sheets. The ROYCO 756/756A data sheet is not listed here: its four “typical” viscosity entries are the specification limits (4.90, 13.2, 600 and 2500), not measurements.

MIL-PRF-5606 — Viscosity by Temperature

Temp (°C)	Temp (°F)	Kinematic (mm²/s)	Dynamic (mPa·s)	Basis

Values from the piecewise ASTM D341 interpolation through the six NADC measurements. Dynamic viscosity uses the density fit and is shown only from 38 °C to 204 °C. “Interpolated, no measurement in span” marks temperatures between −40 °C and 38 °C.

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. The blue series on the charts and the MIL-PRF-23699 columns below use the NIST IR 8263 Table B4 dynamic viscosity (generic to the specification, 16.89–126.85 °C) and the NIST IR 8263 density from the MIL-PRF-23699 density page; MIL-PRF-23699 kinematic viscosity is derived as ν = μ/ρ. See also the sister page MIL-PRF-23699 Dynamic and Kinematic Viscosity. Over the temperatures where both have data, MIL-PRF-23699 is the more viscous fluid at the cool end of the overlap, and the ratio in the table falls as temperature rises until it drops below 1 at the hot end, where MIL-PRF-5606 becomes the more viscous fluid.

Temp (°C)	Temp (°F)	5606 kinematic (mm²/s)	23699 kinematic (mm²/s)	Ratio 23699 / 5606	5606 dynamic (mPa·s)	23699 dynamic (mPa·s)

MIL-PRF-5606 values use the piecewise D341 interpolation of the NADC-79248-60 measurements, −54 to 204 °C (dynamic: 38 to 204 °C). MIL-PRF-23699 dynamic values are linearly interpolated from NIST IR 8263 Table B4, 16.89 to 126.85 °C only; its kinematic values are derived as μ/ρ with the density from the MIL-PRF-23699 density page (measured 5–70 °C, linearly extrapolated above 70 °C). “—” means the fluid has no data at that temperature (extrapolated viscosity values are deliberately not used). The datasets come from different sources, labs and eras, 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. Tables 1 and 2 (MIL-H-5606 columns), 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. Table II viscosity limits.
NYCO, Hydraunycoil FH 51 Technical Data Sheet (TDS_FH51-1E11), 2020. aircraftspruce.com/catalog/pdf/FH51TDS.pdf. Typical kinematic viscosity (ASTM D445).
ExxonMobil, Mobil Aero HF Series product page. mobil.com. Typical kinematic viscosity; HF vs HFA column assignment unverified.
Chemsol, MIL-PRF-5606H typical properties sheet, July 2011. Chemsol TDS. Typical kinematic viscosity; distributor sheet with garbled labels, low confidence.
Chevron, Hydraulic Oil 5606 Product Data Sheet, Jan 2024. Chevron PDS. Typical kinematic viscosity (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. Viscosity entries equal the specification limits; not plotted as typicals.
Bruno et al., Thermophysical Properties of Polyol Ester Lubricants, NIST IR 8263, 2019, doi.org/10.6028/NIST.IR.8263, Table B4 (MIL-PRF-23699 dynamic viscosity) and Table 23 (MIL-PRF-23699 density). MIL-PRF-23699 comparison data, as used on MIL-PRF-23699 General Properties and MIL-PRF-23699 Density (also the MIL-PRF-23699G specification and typical kinematic viscosity values).

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 or specification limits.

MIL-PRF-5606 Dynamic and Kinematic Viscosity

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