Oldsmobile recommends that you change the oil filter at the same time you change the oil. Instead of recommending a time interval between oil and oil filter changes, the 2003 Alero relies on the GM Oil Life System to notify you when a change is due. This system counts engine revolutions and monitors the engine temperature to determine when to flash the "CHANGE OIL" light. You can change the oil and filter yourself. For the Alero V6, you'll need an oil filter wrench, but not for the L4 engine, which has an internal oil filter.
Park the car on a level surface. Loosen the engine oil refill cap enough to allow in some air. This helps the oil drain. Remove the oil drain bolt at the bottom of the engine and let the engine drain for five minutes before removing the oil filter.
Locate the oil filter. The Alero L4 engine uses an internal oil filter, so it might not be immediately evident. The filter is in the front center of the bottom of the engine. For the L4, it's under a black cover that has a hexagonal top for removal with a wrench. On the V6 engine, use an oil filter wrench that fits a PF47 filter (using ACDelco parts). Turn the wrench counterclockwise in both cases. Don't put your face under the filter or filter cover; either one will be full of oil.
Peel the rubber O-ring seal off the engine's oil filter cavity. Clean remaining seal residue off the engine with a rag.
Coat both sides of a new O-ring seal with clean oil. For the L4 engine, you can use either an ACDelco PF458G or PF457G. For the V6, use either a PF47 or PF47E. Set the new O-ring into the engine cavity, set the filter in place and screw on the black cover. For the V6, screw on the new filter until you feel resistance. Then, use the oil filter wrench to turn an additional two-thirds of a rotation. In case you're using a torque wrench, don't tighten the cover or screw-on filter more than 18 foot-pounds.
