Lexus IS 250C 2014 Manual page 557

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 ILSAC (International Lubricant Standardization and Approval
Committee) Certification Mark is added to some oil containers to help
you select the oil you should use.
6-1. Specifications
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