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SAE Viscosity Grade Chart

How to read SAE J300 engine oil and SAE J306 gear oil viscosity grades, with the 100 °C kinematic viscosity range that defines each high-temperature grade.

Ref FA-0088SAE J300SAE J306

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

SAE viscosity grades describe how thick an oil is at set temperatures. They say nothing about additive quality; that comes from the API, ACEA or OEM specification on the label. SAE J300 covers engine oils. SAE J306 covers axle and manual transmission gear oils. The two scales are separate: an SAE 90 gear oil and an SAE 40 engine oil can have similar viscosity.

How to read it

A multigrade such as 15W-40 has two parts. The number with W (winter) is the cold rating, based on cold cranking and pumping tests: lower numbers flow better when cold. The second number is the hot rating, based on kinematic viscosity at 100 °C and, for engine oil, high-temperature high-shear (HTHS) viscosity at 150 °C. A 15W-40 must meet both the 15W cold limits and the 40 hot limits.

High-temperature grades

Grade	Oil type	Kinematic viscosity at 100 °C (cSt)
8	Engine	4.0 to under 6.1
12	Engine	5.0 to under 7.1
16	Engine	6.1 to under 8.2
20	Engine	6.9 to under 9.3
30	Engine	9.3 to under 12.5
40	Engine	12.5 to under 16.3
50	Engine	16.3 to under 21.9
60	Engine	21.9 to under 26.1
80	Gear	7.0 to under 11.0
85	Gear	11.0 to under 13.5
90	Gear	13.5 to under 18.5
110	Gear	18.5 to under 24.0
140	Gear	24.0 to under 32.5
190	Gear	32.5 to under 41.0
250	Gear	41.0 and up

Engine oil winter grades are 0W, 5W, 10W, 15W, 20W and 25W. Gear oil winter grades include 70W, 75W, 80W and 85W.

Key points

Use the grade and the performance specification the OEM lists for the unit and climate. Both matter.
Low-viscosity grades such as 0W-16 and 0W-20 are only for engines designed for them.
Heavy-duty diesel oils carry API C-series categories (such as CK-4 or FA-4). FA-4 oils have lower HTHS and are not backward compatible with all engines.
Gear oils also carry API GL categories. GL-5 oils are not suitable for some manual transmissions that require GL-4.

Common mistakes

Assuming a higher number always means "better protection."
Comparing gear oil and engine oil grades as if they were one scale.
Choosing by viscosity grade and ignoring the API or OEM specification.

Governing standards: SAE J300 (engine oil viscosity classification); SAE J306 (automotive gear lubricant viscosity classification). API and OEM specifications for performance.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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