• International acceptance benefits customers, manufacturers, and marketers.
• The number in the product name for most products represents the viscosity of an industrial oil, which is often the lubricant grade recommended by the equipment manufacturer.
• Conversion from one viscosity measurement to another is virtually eliminated.

Automotive engine and gear oils are not classified using the ISO measurement system. They continue to be described by the Society of Automotive Engineers (SAE) viscosity classifications (see Automotive Lubricants Section).

The table below shows the kinematic viscosity limits for each ISO Viscosity Grade. Each viscosity grade is 50% higher in viscosity than the preceding viscosity grade. These limits are set at a 10 percent tolerance level above and below the mid-point of a grade. Any product with a viscosity outside these tolerance levels is not a recognized ISO Viscosity Grade.



Viscosity System for Industrial Fluid LubricantsA – ASTM D2422 – 97 (2013)
Viscosity System Grade Identification	Mid-Point Viscosity, cSt (mm2/s) at 40.0°C	Kinematic Viscosity Limits, cSt (mm2/s) at 40.0°C B,C
		min	max
ISO VG 2	2.2	1.98	2.42
ISO VG 3	3.2	2.88	3.52
ISO VG 5	4.6	4.14	5.06
ISO VG 7	6.8	6.12	7.48
ISO VG 10	10	9.00	11.0
ISO VG 15	15	13.5	16.5
ISO VG 22	22	19.8	24.2
ISO VG 32	32	28.8	35.2
ISO VG 46	46	41.4	50.6
ISO VG 68	68	61.2	74.8
ISO VG 100	100	90.0	110
ISO VG 150	150	135	165
ISO VG 220	220	198	242
ISO VG 320	320	288	352
ISO VG 460	460	414	506
ISO VG 680	680	612	748
ISO VG 1000	1000	900	1100
ISO VG 1500	1500	1350	1650
ISO VG 2200	2200	1980	2420
ISO VG 3200	3200	2880	3520

A This system implies no evaluation of quality.
B This system is used in ISO 3448.
C If 40°C is not the temperature used when determining the viscosity (as is sometimes the case with very viscous fluids) then the related viscosity at 40°C shall be established by using Viscosity Temperature charts found in ASTM D341.

The American Gear Manufacturers Association (AGMA) used to have a numbering system to define gear oil viscosity required for various gear lubrication applications. AGMA is currently using ISO viscosity grade classifications, but these AGMA Lubricant Numbers are still sometimes stamped on the manufacturer’s metal name plate. ISO viscosity grades and former AGMA grades are cross-referenced in the table below.

NOTES:
* The preferred unit for kinematic viscosity is mm²/s, commonly referred to as centistoke (cSt).

• TURBOFLO™ R&O can be used where AGMA Inhibited (rust and oxidation inhibited) Gear Oils are required.
• ENDURATEX™ EP, ENDURATEX™ XL Synthetic Blend and ENDURATEX™ Synthetic EP gear oils can be used where AGMA Antiscuff (formerly known as Extreme Pressure or EP) Gear Lubricants are required.
• ENDURATEX™ Mild Worm Gear oils, which contain special lubricity additives, can be used where AGMA Compounded Gear oils are required.
• Automotive gear oils, such as TRAXON™, are defined by the SAE for viscosity and the API for quality. These oils can be used in gear boxes but industrial gear oils formulated to meet former AGMA requirements cannot be used in automotive differentials or transmissions.
• SYNDURO™ SHB is suitable for many gear oil applications such as worm gears and helical gear boxes and has an excellent FZG Failure Load Stage of 12+. For those applications that are subjected to heavy loads or shock loading and require an AGMA Antiscuff type of fluid, ENDURATEX™ Synthetic EP is recommended.

Viscosities designated by various organizations may be compared as shown in the Viscosity Equivalents table (seen below). This is strictly a viscosity comparison and should not be construed as a quality level comparison.

ISO VG – Viscosity measurement in centistokes (cSt) at 40°C.

AGMA – Viscosity grades as formerly designated by the American Gear Manufacturers Association.

SAE – Society of Automotive Engineers viscosity measurement for automotive engine and gear oils e.g. SAE 30, SAE 90, etc.

How to use the chart:

If a manufacturer requires an SAE 20 oil for a piece of equipment, go to the SAE viscosity column and follow across horizontally to the left to read an ISO VG of 46.

Comparison of ISO/AGMA/SAE Viscosities at 40˚C

NOTE:

• Read horizontally.

• Equivalence is in terms of viscosity at 40˚C only.

• Viscosities of SAE engine oils based on a VI of 150, an estimated average of current Passenger Car Motor Oil and Heavy-Duty Engine Oil products.

• Viscosities of SAE gear oils based on a VI of 130, an estimated average of current Automotive Gear products.

• Viscosity limits are approximate: for precise data, consult ISO, AGMA and SAE specifications.

• SAE W grades are represented only in terms of approximate 40°C viscosity. For low temperature limits, consult SAE specifications.