Select a gear oil by duty

Most oil tables let you filter by viscosity grade. That only helps if you already know the grade you need. This works the other way round: describe the gearbox, and it applies ANSI/AGMA 9005-F16 Annex B and Annex C to say which lubricants fit.

Gear type

Bulk oil operating temperature, °C

Pitch line velocity, m/s

Pour point at or below, °C

Only values that appear in the table. 9005-F16 cl. 7.1.4 wants the pour point 5 °C below the coldest expected start-up, which is the second figure.

Flash point at or above, °C

The standard's own floor is 180 °C up to VG 68 and 200 °C above; choose higher if the duty needs it.

Driving unit (optional)

Driven unit (optional)

Shock loading selects the lubricant class from Annex C Table C.1. Leave blank to see every class.

These annexes are guidelines, and say so. Annex B applies “in the absence of gearbox manufacturer recommendations, specific application standards, or a rigorous EHL analysis”. A manufacturer’s recommendation outranks this page, and an elastohydrodynamic analysis (AGMA 925) outranks both.

Annex B assumes the oil holds its viscosity over the drain interval, and that operating temperature is roughly 45 °C above ambient.
Consult gear, bearing and lubricant suppliers whenever the indicated grade falls below VG 68 or above VG 680.
Above 30 m/s, 9005-F16 refers you to ANSI/AGMA 6011.
Viscosity at temperature is computed by ASTM D341 as set out in AGMA 955-A22 Annex G.3, from the published 40 °C and 100 °C values. It is a correlation fitted to two points, and below the pour point it is arithmetic rather than physics.