Toyota TUNDRA Manual page 603

Oil viscosity (0W-20 is explained here as an example):
• The 0W in 0W-20 indicates the characteristic of the oil which allows cold
startability. Oils with a lower value before the W allow for easier starting
of the engine in cold weather.
• The 20 in 0W-20 indicates the viscosity characteristic of the oil when the
oil is at high temperature. An oil with a higher viscosity (one with a
higher value) may be better suited if the vehicle is operated at high
speeds, or under extreme load conditions.
How to read oil container label:
The International
Specification Advisory Commit-
tee (ILSAC) Certification Mark
is added to some oil containers
to help you select the oil you
should use.
Lubricant
9-1. Specifications
603
9