fluid type for A-518

but my transmission guy also said no to synthetics in my transmission? i think he is one of those guys who think synthetics do more harm then good, cause i do not see why i couldnt run a synthetic in this transmission? I was told dexronVI by a smart canadian builder i know, and others have told me the valvoline max life atf is the best choice? even tho its brand new? thats whats got me leary bout running the max life atf, its brand new but valvoline claims the max life atf works great in new and older transmissions? i have heard alot of good things about valvolines max life line, there oils and there atf.