Cadillac cts User Manual

Page of 435
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When to Add Engine Oil
If the oil is at or below the lower mark, then you’ll need
to add at least one quart of oil. But you must use the
right kind. This part explains what kind of oil to use. 
For engine oil crankcase capacity, see “Capacities and
Specifications” in the Index.
NOTICE:
Don’t add too much oil. If your engine has so
much oil that the oil level gets above the upper
mark that shows the proper operating range,
your engine could be damaged.
The engine oil fill cap is located in the center of the
engine compartment. See “Engine Compartment
Overview” in the Index for more information 
on location.
Be sure to fill it enough to put the level somewhere in
the proper operating range. Push the dipstick all the way
back in when you’re through.