Which oil and filter for 5.3??

[vetteboy86]

I was wondering if any had comments about the oil I shoudl run in my 04 silverado? I am not sure if it has synthetic in it right now, but thought that synthetic might have been factory fill.

So give me the low down of switching from convential to synthetic and vice versa?? I think synthetic is better oil, however I am changing oil like crazy before my vehicles are due. The mobil 15k mile in the vette rarely sees 3k miles

Thanks,
Craig