I do it myself. I use Royal Purple 10W30 and WIX filters. Do not use fram filters, they are junk. These trucks run rich and carbon up easily. Mobile 1 is a good, readily available synthetic, but conventional oil is ok too...just make sure and change it, religously. Use a good quality oil filter. Sorry Jdelp, I have seen too many tests on filters. Fram's are junk. You are right on the oil changes. I paid $13 at wal-mart to have mine done, and they didn't want me watching. Never again. Also took my Caddy to a Penzoil place. They told me my tranny needed to be flushed. I asked them to show me. They showed me engine oil. The 03 CTS has a sealed tranny. no dipstick, and like the D2's, if you open the drain plug without it running, fluid just pours out. I got that change free, never to return. Point: it isn't worth the 30 minutes you save to know it was done right by your hands....

 

How often should you change it..

 

3000 miles (or 3 months, whichever comes first with conventional.) time doesn't matter with synthetics.

 

hijacked....

 

Did you get your codes cleared? pulling the battery is not the best idea. Your ECU will have to re-learn your driving habits and you will get poor performance until then. You will need your radio code and posssibly have to re-set your temp controls.

I really feel like what you had going on was due to a bad battery. Get the codes cleared and see if anything comes back.