as title, should I go back to mazda for factory 5w20 or any other? I need some names pls.

Your help is appreciated!

 

You should check out the numerous other Oil threads already on the forums.

 

True about the search request...

However, hidden in all that, is a possibility that the original oil has some special formulation, that should not be changed-out prematurely. True? Beats me...

Something that's been curious to me,

My first scheduled change was:
"5 0000-77-5W20-QT SAE 5W-20 SUP PR MTR"

My second scheduled change was:
"5 O0114 CASTROL GTX 5W20"

Now, Castrol GTX happens to be my favorite brand & I have a case of CASTROL GTX 5W20 sitting in the garage with "FOR RX-8 ONLY" written on it. But my dealership doesn't know that. Have they changed to Castrol at some time inbetween my two pit stops? Dunno. Was there something special with the oil used in my first pit stop? Also, dunno.

So, what I'm saying is, I'm answering your question by asking you two questions...

1) Is there something special with the original oil?

2) Is there something special with the pit stop #1 oil?

 

You only need to follow the manual's recommendation. 5W20 non-synthetic is fine, just be sure to get one with an API Service Rating of SL or higher. Common national brands will work fine, i.e. Castrol, Pennzoil, Havoline, etc.

I'm using Pennzoil, and perfectly comfortable with that.

 

I use the Mazda oil in the black bottles. Just, because...I have it.

 

the mazda mechanic told me never to use synthetic oil cuz it would mess up the engine, is that true?

 

You should have stopped there.
Though you imply it, this is not in the manual. (In NA) 5W20 is required; there is no mention of synthetic whatsoever in this regional owner's manual.
At least this is good advice.