Lexus GS430 User Manual page 553

The amount of engine oil consumed depends on the
viscosity of the oil, the quality of the oil and the way the
vehicle is driven.
More oil is consumed under driving conditions such as high
speeds and frequent acceleration and deceleration.
A new engine consumes more oil, since its pistons, piston rings
and cylinder walls have not become conditioned.
Oil consumption: Max. 1.0 L per 1000 km (1.1 qt./600 miles,
0.9 lmp·qt./600 miles).
When judging the amount of oil consumption, keep in
mind that the oil may have become diluted, making it
difficult to judge the true level accurately.
For example, if a vehicle is used for repeated short trips and
consumes a normal amount of oil, the dipstick may not show
any drop in the oil level at all, even after 1000 km (600 miles)
or more. This is because the oil is gradually becoming diluted
with fuel or moisture, making it appear that the oil level has not
changed.
The diluting ingredients evaporate out when the vehicle is then
driven at high speeds, as on an expressway, making it appear
that oil is excessively consumed after driving at high speeds.
Importance of engine oil level check
One of the most important points in proper vehicle
maintenance is to keep the engine oil at the optimum level so
that oil function will not be impaired. Therefore, it is essential
that the oil level be checked regularly. Lexus recommends that
the oil level be checked every time you refuel the vehicle.
NOTICE
Failure to check the oil level regularly could lead to
serious engine trouble due to insufficient oil.
For detailed information on oil level check, see "Checking the
engine oil level" on page 530.
ENGINE
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