Synthetic Oil

I have heard the same thing, once you start the synthetic's you gotta stick with them... My dad does that in his vette, and hes the one who told me that... Maybe its just an "Urban myth"...

No you can switch back and forth if you want to, just don't know why you would want to less protection, but you can.

Castrol, mobil, and Royal Purple all have 800 #'s on their bottles. I called, and every manufacturer said there is no harm in switching back and forth. They said you can top off w/ regular oil if you are a quart low. They also said you can go around 6000 mi. between changes, but have to still change the filter at 3000 mi. Of course add a quart if you change the filter.