I've used both for about equal amounts of miles, and I have to say, Valvoline holds up better in shift quality, and results in much less (trace amounts) metal swarf on the magnet. Both were done as drain and fills (three total for redline) every 20k, Valvoline Maxlife was always bright cherry red after 20k, Redline started darkening significantly and always left quite a bit of fuzz on the magnet. Maxlife never really seemed to degrade much as it aged, D6 started getting really choppy and rough about 15k miles in.
Sticking with Maxlife from here on out, still can't believe $18 fluid significantly outperforms $60 fluid, whatever magic juice they're putting in it just works wonderfully.
Sticking with Maxlife from here on out, still can't believe $18 fluid significantly outperforms $60 fluid, whatever magic juice they're putting in it just works wonderfully.