My manual recommends mineral oil. Nissan doesnt say not to use synthetic, but if they recommend mineral oil, there must be a reason.
Then again I guess as long as the oil has the API certified label, then its all good.

As for extended oil changes with a synthetic, doesnt oil become contaminated with combustion by products?
A synthetic would still have to be changed as frequently as mineral oil. At least I would anyway.

I switched to synthetic in my 95 Protege, and shortly after started experiencing oil leaking onto my spark plugs.
I am not sure if the synthetic caused this, or if it would have happened anyway.
However the experience has me questioning synthetic oil.

In Canada, Royal Purple motor oil does not have the API certification stamp, therefore would not qualify as a suitable oil.