2009 Cadillac CTS Owner's Manual - Page 325

When to Add Engine Oil See Engine Compartment Overview on page 5-14 for the location of the engine oil fill cap. If the oil level is within the cross-hatched area at the tip of the dipstick, add at least one quart/liter of the recommended oil. This section explains what kind of oil to use. For engine oil crankcase capacity, see Capacities and Specifications on page 5-133. Notice: Do not add too much oil. If the engine has so much oil that the oil level gets above the proper operating range and into the upper cross-hatched area on the dipstick, the engine could be damaged. Add enough oil to put the level somewhere in the proper operating range. Push the dipstick all the way back in when through. 5-19