do a search... it's been answered to death...
oh wait, this is a new board :wave2:
I change my oil AND filter every 3000 street miles... I use full synth all the time. Intervals are really dependant on the use of your engine, the filters ability, and the oil you use... If your oil looks like crap after just 1k, then change it. If your oil still looks nice after 4k then don't change it...
I would suggest that if you're running dino or a blend you should keep a closer eye on your oil changes then if you're running full synth.