CX9 doesnt have a rotary and Mazda has been specing 0w20 for the new 2012 Mazda 3 and 2013 Mazda CX5. If 5w20 conventional is spec'd then I would just use a good quality syn for the same weight. There are many choices out there :
PP , Synpower , QSUD , M1.
For the money I'd look into MC 5w20 syn blend ...... supposedly has around 60% syn content , one of the highest.
Or you can use VWB, PYB , Mobil Super 5000.