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So what makes you think that "genuine toyota motor oil" is any more kosher with the warranty than royal purple? Do you think that if there is a difference, Mazda will void your warranty anyway by using oil made for a competing manufacturer's cars?

 

When I went to the oil shop for the oil change I changed my mind beause of the warranty issues about synthetic and asked for regular 5w20 oil if available and they told me they have toyota genuine brand oil...do you think that going 5w20 is bad ?? I can assume, a metering pump injects oil using pressure and injector opening "internal diameter"... and I was thinking if I use a higher viscosity oil it will change the oil injection flow, we know already a higher viscosity fluid will take longer to pass into a told diameter instead of a thinner oil....

 

You thought part of it through, but not all of it.

The motor oil you use isn't just for injection into the engine. It's also used, appropriately, by the bearings, to keep THEM from wearing. And 5w20 isn't good enough, it's too thin.

Since 4-stroke oil isn't the best to burn anyway, the best solution is to get the SOHN adapter and run a separate feed of clean burning 2-stroke oil through the oil injectors into the combustion chamber instead of the constantly dirty 4-stroke.