I asked the mechanic at Nissan if I can switch back and forth from sythetic to reg. oil he said I can. I have a stock 06 Z is this true?

 

I don't see why not...

 

No no please. No more best motor oil threads.

 

It can be done but it's usually not a good idea to do so. Different types of oil have different additive packs in them and different base stocks and switching from one to another can have adverse effects.

If you've been running regular oil and wish to go synthetic then make the switch and stay on synthetic. If you've been on synthetic and feel the need to go back then go back and stay on regular oils. I've seen situations where an engine will start burning oil after changing brands or types of oil and often time will not stop even after being switched back. It's really strange but with the detergents and additive packs strange things can happen.

I'm a strong beliver in putting whatever oil you plan on running in your car in there from the first oil change and sticking with it.