Cadillac 1993 Fleetwood Owners Literature page 277

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Oils with these words on the container will help you save fuel.
This doughnut-shaped logo (symbol) is used on most oil containers to
help you select the correct oil.
You should look for this on the oil container, and use only those oils that
display the logo.
GM Goodwrench@ oil (in Canada, GM Engine Oil) meets all the
requirements for your vehicle.
Engine Oil Additives: Don't add anything to your oil. Your Cadillac
dealer
is
ready to advise if you think something should be added.
When to Change Engine Oil: Your vehicle is equipped with an engine oil
life indicator (EOLI) feature. Oil change intervals are determined by the
EOLI and will usually fall at, or between, the two recommended
alternative intervals of 3,000 miles (5,000 kilometers) and 7,500 miles
(12,500 kilometers), but could be shorter than 3,000 miles (5,000
kilometers) under some very severe driving conditions shown in Schedule
I. The system will also indicate the need for an oil change if 7,500 miles
(12,500 kilometers).
When the oil life index reaches 0, the "CHANGE OII? light come on.
This indicates that no oil life remains and the oil should be changed as
soon as possible, but certainly within the next 200 miles (320 km).
The EOLI will not detect excessively dusty conditions or engine
malfunctions which may effect the oil. If you drive in dusty areas, change
the engine oil after every 3,000 miles (5,000 kilometers) or 3 months
(whichever comes first), unless instructed to do so sooner by the
"CHANGE O W light.
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