MIL-PRF-6083 Viscosity: Calculator & Chart

MIL-PRF-6083 Kinematic Viscosity Chart

MIL-PRF-6083 kinematic viscosity vs temperature in degrees F, four product lots and specification limits, compared with MIL-PRF-5606

At 104 °F (40 °C), MIL-PRF-6083 is about 14 to 16 mm²/s (cSt) on current data sheets; at −65 °F (−54 °C) it is about 2900 to 3500 mm²/s. The limits are 13.2 mm²/s minimum at 40 °C and 3300 mm²/s maximum at −54 °C. Y-axis is logarithmic.

There are no measurements for this page. Every point is a single-lot “typical” value printed on a manufacturer data sheet. Each curve is a piecewise ASTM D341 interpolation through the four printed points of one product (three for ROYCO 783), drawn only from −54 °C to 100 °C (ROYCO 783: to 40 °C); nothing is extrapolated. No data sheet gives a value between −40 °C and 40 °C, so the dashed part of each curve is interpolation only. The lots are not averaged.

Circles are manufacturer typical values (not measurements), one colour per product lot. Black crosses are the limits of MIL-PRF-6083G Table I (maximum at −54 and −40 °C, minimum at 40 and 100 °C), not measurements. Older revisions of the specification (6083F and earlier) had different limits. The blue MIL-PRF-5606 curve and circles are the measured MIL-H-5606 values from NADC-79248-60 Table 1 (1980 lot, revision not stated), copied unchanged from the MIL-PRF-5606 viscosity page.

Data from: MIL-PRF-6083G Table I (limits); product data sheets listed under Sources; NADC-79248-60 (Conte & Hammond, 1980), DTIC ADA081597, Table 1 (MIL-PRF-5606 comparison).

Toggle data sets by clicking the legend.

MIL-PRF-6083 Viscosity Calculator

Degrees (°F):

Degrees (°C):

Kinematic Viscosity, RADCOLUBE RHP6083 (2025 data sheet)

mm²/s (= cSt):

Centistokes (cSt):

Stokes (cm²/s):

m²/s:

in²/s:

ft²/s:

Other data sheet lots (cSt)

RADCOLUBE RHP6083 (2020):

Brayco Micronic 783 (2009):

ROYCO 783 (2016, to 40 °C):

MIL-PRF-5606 (comparison)

Kinematic (cSt):

Ratio 6083 / 5606:

Kinematic viscosity is valid −54 °C to 100 °C (−65.2 °F to 212 °F), atmospheric pressure, from the piecewise ASTM D341 interpolation through the 2025 RADCOLUBE RHP6083 data sheet values. Between −40 °C and 40 °C it is interpolation only. The other lots are shown where their own four data sheet points cover the temperature (ROYCO 783 to 40 °C only); “—” means no data. These are single-lot typical values, not guaranteed values for any drum. The MIL-PRF-5606 row is valid −54 °C to 204 °C; “—” means no data.

Viscosity of MIL-PRF-6083 Preservative Hydraulic Fluid

About This Data

MIL-PRF-6083 (NATO C-635, Military Symbol OHT) is a rust-inhibited petroleum hydraulic fluid for preservation and operation, used from −54 °C to 135 °C. It is the rust-inhibited relative of MIL-PRF-5606. See the MIL-PRF-6083 general properties page for the specification limits and products.

The values on this page are the “typical results” printed on four data sheets: RADCOLUBE RHP6083 (Radco Industries, 2025 and 2020 sheets), Castrol Brayco Micronic 783 (2009) and ROYCO 783 (LANXESS, 2016). Each gives kinematic viscosity at −54, −40, 40 and 100 °C (ASTM D445); ROYCO 783 gives no 100 °C value. They are single-lot values with no stated uncertainty, and the lots differ: at −54 °C from 2859 to 3450 mm²/s, at 40 °C from 13.6 to 15.6 mm²/s. The RADCOLUBE RHP6083 2025 sheet is used for the calculator because it is the newest sheet and it states MIL-PRF-6083G.

The smooth curve is a piecewise ASTM D341 interpolation: between neighbouring printed 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 printed point. A single D341 line through all four points of one product was not used because it misses the points by up to about 20 % (the fluid contains a polymeric viscosity-index improver). The span from −40 °C to 40 °C has no data point inside it, so values there are interpolation only. Nothing is extrapolated outside −54 °C to 100 °C.

There is no dynamic (absolute) viscosity chart for MIL-PRF-6083. Dynamic viscosity needs the density at each temperature, and the only density values found are single values at 15.6 °C (see the general properties page). For fluids that do have density data, see MIL-PRF-5606 viscosity and MIL-PRF-83282 viscosity. To convert, see below.

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-6083 — Manufacturer Typical Viscosity (not measurements)

Product (data sheet)	Temp (°C)	Temp (°F)	Kinematic viscosity (mm²/s), typical
RADCOLUBE RHP6083, 2025 data sheet	−54	−65.2	2859
RADCOLUBE RHP6083, 2025 data sheet	−40	−40.0	559
RADCOLUBE RHP6083, 2025 data sheet	40	104.0	15.6
RADCOLUBE RHP6083, 2025 data sheet	100	212.0	5.45
RADCOLUBE RHP6083, 2020 data sheet	−54	−65.2	2916
RADCOLUBE RHP6083, 2020 data sheet	−40	−40.0	600
RADCOLUBE RHP6083, 2020 data sheet	40	104.0	15.4
RADCOLUBE RHP6083, 2020 data sheet	100	212.0	5.5
Castrol Brayco Micronic 783 (2009 sheet)	−54	−65.2	3450
Castrol Brayco Micronic 783 (2009 sheet)	−40	−40.0	650
Castrol Brayco Micronic 783 (2009 sheet)	40	104.0	13.6
Castrol Brayco Micronic 783 (2009 sheet)	100	212.0	4.7
ROYCO 783 (2016 sheet)	−54	−65.2	3100
ROYCO 783 (2016 sheet)	−40	−40.0	685
ROYCO 783 (2016 sheet)	40	104.0	13.8

Single-lot typical values from the four data sheets listed under Sources, copied as printed. No uncertainty is stated. The ROYCO 783 sheet has no 100 °C value. Data sheet values for the same fluid type differ from lot to lot.

Specification Limits (MIL-PRF-6083G Table I)

Temp (°C)	Temp (°F)	MIL-PRF-6083G Table I limit (mm²/s)	RHP6083 2025 typical (mm²/s)
−54	−65.2	≤ 3300 (max)	2859
−40	−40.0	≤ 700 (max)	559
40	104.0	≥ 13.2 (min)	15.6
100	212.0	≥ 4.6 (min)	5.45

These are acceptance limits for the fluid, not measurements. The last column is the RADCOLUBE RHP6083 2025 typical value at the same temperature. Older revisions of the specification had different limits; for example the 2009 Castrol sheet, which cites MIL-PRF-6083F, lists 800 mm²/s maximum at −40 °C, 3500 maximum at −54 °C and 13 minimum at 40 °C.

MIL-PRF-6083 — Viscosity by Temperature

Temp (°C)	Temp (°F)	RHP6083 2025	RHP6083 2020	Brayco 783	ROYCO 783	MIL-PRF-5606 (NADC)	Basis
−54	−65.2	2859.0	2916.0	3450.0	3100.0	2000.0	Typical (printed on data sheets)
−40	−40.0	559.0	600.0	650.0	685.0	500.0	Typical (printed on data sheets)
−30	−22.0	278.4	292.8	300.3	313.8	245.5	Interpolated, no measurement in span
−20	−4.0	153.1	158.5	155.9	161.8	133.7	Interpolated, no measurement in span
−10	14.0	91.37	93.37	88.98	91.81	79.33	Interpolated, no measurement in span
0	32.0	58.33	59.00	54.88	56.36	50.46	Interpolated, no measurement in span
10	50.0	39.38	39.51	36.07	36.90	34.00	Interpolated, no measurement in span
20	68.0	27.86	27.77	25.00	25.49	24.04	Interpolated, no measurement in span
30	86.0	20.50	20.33	18.10	18.41	17.70	Interpolated, no measurement in span
40	104.0	15.60	15.40	13.60	13.80	13.58	Typical (printed on data sheets)
50	122.0	12.55	12.46	10.91	—	11.01	Interpolated between typical points
60	140.0	10.30	10.27	8.928	—	9.102	Interpolated between typical points
70	158.0	8.605	8.61	7.442	—	7.648	Interpolated between typical points
80	176.0	7.296	7.324	6.301	—	6.52	Interpolated between typical points
90	194.0	6.269	6.311	5.409	—	5.63	Interpolated between typical points
100	212.0	5.45	5.5	4.7	—	4.925	Typical (printed on data sheets)

Kinematic viscosity in mm²/s (= cSt) from the piecewise ASTM D341 interpolation through each product’s printed points. “—” means that data sheet gives no data at that temperature. The MIL-PRF-5606 column is the 1980 NADC measured data (−54 to 204 °C), interpolated the same way. “Interpolated, no measurement in span” marks temperatures between −40 °C and 40 °C; the 40 to 100 °C span is also interpolated between two printed points.

MIL-PRF-6083 vs MIL-PRF-5606

MIL-PRF-6083 is the rust-inhibited petroleum fluid; MIL-PRF-5606 is the petroleum hydraulic fluid for aircraft, missiles and ordnance. On these data the 6083 lot (RADCOLUBE RHP6083, 2025) is about 11 to 43 % more viscous than the 1980 NADC 5606 lot, most of all at −54 °C. The two come from different labs and eras and different lots, so small differences should not be over-interpreted. The 6083G limits are also looser than the 5606H limits at low temperature (3300 vs 2500 mm²/s at −54 °C; 700 vs 600 at −40 °C). See also the MIL-PRF-5606, MIL-PRF-83282 and MIL-PRF-46170 general pages.

Temp (°C)	Temp (°F)	5606 kinematic (mm²/s)	6083 kinematic, RHP6083 2025 (mm²/s)	Ratio 6083 / 5606
−54	−65.2	2000.0	2859.0	1.43
−40	−40.0	500.0	559.0	1.12
−20	−4.0	133.7	153.1	1.14
0	32.0	50.46	58.33	1.16
20	68.0	24.04	27.86	1.16
40	104.0	13.58	15.60	1.15
60	140.0	9.102	10.30	1.13
80	176.0	6.52	7.296	1.12
100	212.0	4.925	5.45	1.11

MIL-PRF-6083 values use the piecewise D341 interpolation of the RADCOLUBE RHP6083 2025 data sheet values. MIL-PRF-5606 values use the same interpolation of the measured NADC-79248-60 Table 1 points, copied unchanged from the MIL-PRF-5606 viscosity page. Ratios are computed from these two columns.

Sources

US Department of Defense, MIL-PRF-6083G, Performance Specification: Hydraulic Fluid, Petroleum Base, for Preservation and Operation, 26 April 2013. everyspec.com. Table I viscosity limits (printed page 6), accessed 29 Oct 2026.
Radco Industries, Technical Data Sheet for RADCOLUBE RHP6083, MIL-PRF-6083G, product code 23271-G, revision date 15 Aug 2025. radcoind.com TDS. Typical kinematic viscosity (ASTM D445).
Radco Industries, RADCOLUBE RHP6083 Hydraulic Fluid, Petroleum Base, for Preservation and Operation, MIL-PRF-6083G data sheet (undated; qualified 2020). data sheet (Petroleum Service Company copy). Typical kinematic viscosity (ASTM D445).
Castrol, Brayco Micronic 783 Product Data, 16 July 2009, Version 1 (claims MIL-PRF-6083F). Brayco Micronic 783 data sheet. Typical kinematic viscosity (ASTM D445).
LANXESS, ROYCO 783 Preservative Mineral Hydraulic Fluid, Data Sheet, technical information effective 26 May 2016. ROYCO 783 data sheet. Typical kinematic viscosity (ASTM D445), no 100 °C value.
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 1 (MIL-H-5606 column), used only for the MIL-PRF-5606 comparison series.

The data sheet values are single-lot typicals with no stated uncertainty. The NADC report does not state the specification revision or lot of the MIL-H-5606 tested. Searches found no density, specific heat or thermal conductivity data for MIL-PRF-6083, so there are no dynamic viscosity, Prandtl number or other derived pages for this fluid.

MIL-PRF-6083 Kinematic Viscosity

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