How far will the 6F35 go? Most folks threw in the towel early in the life of the vehicle, citing immediate complaints about shift quality, shift flares and shudder. Some of us saw units fail before 20,000 miles for largely unknown reasons. Even once Ford went ahead and rebuilt or replaced units, the same concerns were right back as soon as the adaptive shift strategy took hold. My newer Fusion continues on with its 6F35. Every day is a huge question mark to the integrity of the transmission. I've drained and refilled the transmission nearly 10 times (2-3 times at 3 different intervals) since I've owned the car and I'm nearly positive that fluid maintenance is the only thing keeping it in a plateaued state of functioning since I bought it two years ago at 36k miles. The inconsistent shift quality is the least of my concern most of the time, however a constant shuddering under load along with intermittent severe shift flares (generally only when transmission is cold) This is an expensive transmission. The cheapest I've seen a new 6F35 go for is around $4,000, before installation. I don't want to take the hit on getting rid of the car, especially since I love nearly everything about it (the transmission excluded, of course), however losing some money (negative equity; high mileage:model year) would be less of a hit than buying a new transmission at any point in the car's lifetime. I don't want a change from Mercon LV to be the nail in the coffin for this unit. I've just recently had the latest calibration update performed under Ford's CSP for the throttle body failures. This was primarily an engine calibration update, but I can tell they definitely tweaked a few things in the transmission file. While the newest calibration does seem to offer a slight bit more predictability to the function of the powertrain, it doesn't worry me any less about a premature failure of this transmission. My question is, being that the current software is probably the last update that Ford will release, the only updates come in the form of fluid technology, short of rebuilding the unit using all the latest Sonnax updates. I've seen it repeated over and over that REDLINE D6 with an added dose of LubeGard Red has the remarkable ability to lessen the disconcerting behavior of the 6F35, thereby possibly prolonging its life. I recently stumbled upon a BITOG thread started by a member regarding a collection of people submitting fluid samples to Blackstone in the effort to establish whether the transmission is wearing itself out, leaving the fluid contaminated with aluminum and clutch material or if the ill behavior doesn't seem to be affecting the unit, which would assume that Mercon LV really does just darken for no reason, which I really have a hard time getting on board with. The only part that makes me question all of this is the fact that the '13+ Fusion is still using the 6F35 with some excellent success, along with using Mercon LV. What changed? If I had Ford replace my aging 6F35 tomorrow with a new unit, would it function as well as a 2013+ Fusion's 6F35? TL;DR Do we have any other high mileage 6F35 owners out there that can definitively distinguish that a move away from plain Mercon LV over to Redline D6 with an additive (or similar) was a move for the better in reducing 6F35 operation concerns.