OK, now it's time to install a new filter and refill the crankcase with oil. The General calls for an AC/Delco UPF44 or equivalent filter, and, once again, the brand you use is strictly a matter of personal preference as long as it meets or exceeds the factory spec. Be sure to coat the rubber gasket of the filter with some new oil before installing it. This will ensure a tight fit between the filter and the engine block and prevent any leaks. The factory spec for the filter is to tighten it using 22 lb-ft with a torque wrench. Again, I use the "feel" method here, too. I just hand-tighten the filter about one full turn after the gasket makes contact until it "feels" tight enough, and I've never had any leakage problems using this method.
At this point, most folks lower the car and proceed to fill the motor with new oil, but I feel this is a bit premature. The way I do it is to first level the car, then pour in 6 quarts of new oil, replace the filler cap, and push the dipstick all the way home. I generally give it about 5 minutes to allow the new oil to fill the pan. (CAUTION: Make sure the C5 or C6 is in park if it's an automatic, or in neutral if it's a stick.) Start the engine and let it run for a few minutes, shut it off and check for any leakage around the filter and drain plug; if there are any problems, now's the time to take corrective measures while the car is still elevated. If everything checks out OK, you can reverse the methods you used to elevate the car to get it back on the ground again.
Open the hood and check the oil level with the car sitting on level ground (I use a small bubble level resting on the door sill plate to check for levelness); the oil will probably be a little low, which is normal. Add an additional 1/2 quart of oil if required, start it up and let it run for a few minutes longer, then shut it off and check the oil level again. It should be right on the money now. If it is, the next task is to reset the "oil life" indicator on the DIC.
This is easy to do, and resetting the indicator is necessary so that you'll know when your next oil change is due. For a C5, turn the ignition switch to "on," but do not start the engine (however, this can be done with the engine running in a C6). Press the "trip" button on the DIC so that it cycles through until it displays "oil life" percentage remaining. Press and hold the "reset" button for two seconds. "OIL LIFE REMAIN 100%" should appear on the display. You can shut off the ignition switch or, better yet, start her up and take her out for a spin.
Take the used oil to Auto Zone, Pep Boys, or just about any other national auto parts outlet who will accept it for ecologically-responsible disposal/recycling at no charge. That's all there is to it. So you've saved yourself some money and the job is done right. So why not treat yourself and the family to a pizza with the saved cash? I told you it wasn't a difficult job, didn't I?
Tools Required: low-profile trolley jack, four sturdy jackstands, bubble level, droplight, 15mm wrench or socket w/ ratchet, 5w30 synthetic oil, filter, oil drain pan; optional: gradual-incline Rhino Ramps, FilterMag, magnetic oil pan plug, 1-inch wrench, creeper or mat, latex or nitrile gloves
Time Required: about 1 hour
Parts Source: auto parts store