I waited till 10k for synthetic.

I recommend Castrol GTX 10w30 for regular oil. That stuff is the best.

 

To each his own with oil, but as far a 10K miles to switch, that's a bit much. You really just want to allow your rings to seat a and bearings to sit in before you switch, which at most is about 5K and that's being really really conservative....

Later,
Aj