I second thebman. I haven't get any confirmation or unconfirmation whereas Mazda put special formulated break-in oil at the factory. Lacking this critical information, following the UM seems to be the right thing to do.
Those who think there is no special break-in oil are welcome to elaborate and please provide the proof of your statement.
I wouldn't risk to flush the engine oil too early (<5000 miles), and will certainly not swap to synthetic oil before the engine completely "breaks in", i.e., 10-15 kmiles or so, or the second oil change. Notice that the MRZ engines use many low friction components (low tension piston ring, etc....), that means it might take longer for the engine to wear down into its optimal shape, i.e., when all components seat correctly, fit well to each other, so that the engine could provide a highest possible compression, and lost insignificant oil into the combustion chamber.
Those who think there is no special break-in oil are welcome to elaborate and please provide the proof of your statement.
I wouldn't risk to flush the engine oil too early (<5000 miles), and will certainly not swap to synthetic oil before the engine completely "breaks in", i.e., 10-15 kmiles or so, or the second oil change. Notice that the MRZ engines use many low friction components (low tension piston ring, etc....), that means it might take longer for the engine to wear down into its optimal shape, i.e., when all components seat correctly, fit well to each other, so that the engine could provide a highest possible compression, and lost insignificant oil into the combustion chamber.