Personally I will never use synthetic again. I ran dino oil for a long time in my old ca18det with no problems.
I then decided to switch to synthetic because everyone was telling me how great it is, well long story short it ate through one of my piston rings The synthetic brought foward a problem that the dino oil was hiding but I'm positive if I would have stuck to dino oil I would have gotten ALOT more miles out of that engine.
I learned my lesson, I plan to never make a high milage engine switch over to synthetic or any engine for that matter just to be safe :o