Lexus GS 450h 2008 Owner's Manual page 426

4-3. Do-it-yourself maintenance
■
Recommended viscosity
Outside temperature
■ How to read oil container labels
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.
424
SAE 5W-30 is the best choice for
good fuel economy, and good
starting in cold weather.
If SAE 5W-30 oil is not available,
SAE 10W-30 oil may be used.
However, it should be replaced
with SAE 5W-30 at the next oil
change.