Not sure about first generation Mazda5's with A/T... but US-spec 2nd gen 5's ask for Mazda M5 fluid which is not the same as Mercon V as addressed in various posts on the forum. I believe there is a TSB on that topic too.
I was doing research on this subject about a year ago and called Mobil to ask about their synthetic ATF and was told that for my cars (2014 Mazda5 and a Hyundai needing SP-III ATF) they will not advise using it. I chose Castrol Transmax instead. Their Import multi-vehicle ATF is compatible with transmissions Mazda requiring M5 ATF based on a PDS. Other suitable choices are Idemitsu Type-M and Valvoline MaxLife ATF. Not sure if they are easily available outside of the US.
