Conventional verses synthetic.... while the synthetic is way better, most of them still don't have the zink to protect the camshaft. If it is certified for moden vehicles (ANYTHING you see on wall mart shaf or at juffy lube, or 99.9% of any place you'd look for oil) it won't have enough zink to protect the cam.
The Synthetic is still better than conventional oil though.
The new oil coming out by castrol
http://www.castrol.com/castrol/gener...tentId=7032644 has said zink.