change mine every 4 months (Dec/April/Aug). the every 5K is a good idea too (easy way to remember), but i like to change mine a little more frequently. just use wallymart's supertech oil & filters & have never had a problem. someone told me it was just rebranded penzoil, but i'm not sure if that's true.

on a sidenote, no one i know changes their own oil anymore. they've all farmed it out to the quickie lube spots.