Two years ago, Valvoline MaxLife had a higher viscosity that did not comply with Dexron VI specs, but Valvoline recommended it for use in Dexron VI applications anyway. (As a result, I take Valvoline recommendations with a grain of salt.) But the new formulation of MaxLife appears to be an acceptable replacement for Dexron VI. In their online ATF FAQ, Valvoline states that MaxLife is a synthetic fluid. The old product technical sheet (before the viscosity change) explicitly stated that MaxLife was a synthetic. The new one does not; in fact the word "synthetic" is not even mentioned. I suspect that Valvoline is reserving the right to change to conventional base stocks (or a blend) without issuing a new spec sheet. Who knows if the current FAQ is up-to-date?
I recently bought some MaxLife for my next ATF change replacing Super Tech Dexron VI. With a 40% coupon at Advance Auto, it is cheaper in gallon jugs than Super Tech Dexron VI (only available in quarts at my local WM for $3.97). MaxLife looks like a good Dexron VI clone and there is reasonable likelihood that the base stock is synthetic, while Dexron VI typically (and almost assuredly in the case of Super Tech brand) is only a synthetic blend. My application (a 2003 Mazda MPV) has an OE spec of Mazda M-III fluid (which is reportedly based on Dexron II(E)), so I doubt the choice of Dexron VI vs MaxLife makes much difference anyway. Both are far more shear stable than Dexron III.
For the current MaxLife ATF tech sheet, see
www.valvoline.com/pdf/Maxlife_ATF.pdf.
For the old MaxLife ATF sheet (circa Feb 2008) see http://replay.web.archive.org/20081226212804/http://www.valvoline.com/products/Dexron%20III%20Mercon.pdf.
Unfortunately, the old sheet archived on Internet Archive [dated 2006] does not include a reference synthetic base stocks, but I have a copy I personally archived dated 8-10-08 that reads
"It is formulated with synthetic base stocks, ...".