Good article about Mercon LV.
Mercon LV and Mercon V are not interchangeable is correct and true statement. The dealership can not void your warranty because you did not use "Ford" Mercon LV unless they can prove the fluid you used directly caused the problem should a problem arise. Please refer to the Magnuson-Moss Warranty Act. As long as the fluid you use is equal to or better than the required fluid than you can use that fluid. By this I mean that if you use ATF made by Oil Maker ABC and said ATF is Mercon LV compatible or Mercon LV equivalent than you can use that fluid without fear of voiding warranty. The fluid you use must meet Mercon LV standards. For example: AmsOil makes Synthetic Fuel Efficient Automatic Transmission Fluid (ATL) which is " recommended for automatic transmissions and other applications requiring DEXRON® VI, MERCON® LV, SP or Toyota WS."
If you look at Mercon LV (Ford) specs: http://www.fcsdchemicalsandlubricants.c ... N%20LV.pdf
versus AmsOil ATL specs (at bottom of page): http://www.amsoil.com/storefront/atl.aspx
you will see that they are very similar. Again as long as it is the right TYPE of fluid it doesn't matter the brand. This is not exclusive to motor oil. If you use Mercon V or equivalent made by AmsOil, Valvoline, Mobile 1, etc. your warranty can and will be voided due to failure to use the appropriate fluid if your vehicle requires Mercon LV.
You bring up some good points, but I would like to rebut a few. As far as voiding the warranty, I can almost guarantee that if you go to a dealer with a burned-up transmission and tell them that you used non-Ford fluid (it does not matter if it "should" work or not), they are going to void the warranty. The burden will be on you to prove that it didn't break the tranny. It may not be right or fair, but that is the harsh reality of most dealers and automakers. The only way I could see you getting around it is by either lucking out with an incredibly understanding dealer, or getting the tranny fluid company to go to bat for you. Automatic transmissions are fragile creatures, and most people will be quick to blame a failure on anything that isn't specifically OEM-approved.
As far as the statement about it not mattering what brand of fluid you use, I'm afraid that this is not entirely true. Honda transmissions are a good example - I have anecdotal evidence, both first- and second-hand, of many Honda trannies shifting weird or not performing well when generic fluids that "meet the OEM specs" are substituted for the OEM fluid. Again, it may not be right, but the fact is that there is no universal licensing agency for tranny fluid like there is for motor oil (I am talking about the API). While many non-API approved motor oils may work just fine (Amsoil is a good example), it's not a risk I am willing to take with tranny fluid, especially since no tranny fluid can be certified by anyone other than the company who makes it to begin with - conflict of interest, anyone?
Finally, regarding your next post about fluid change intervals, no automaker that I am currently aware of recommends 30k mile fluid changes - you are right about that. But unlike motor oil, the darkening of transmission fluid is indeed an indication of wear. If you let any vehicle go for 150k and change the tranny fluid, you're going to be hard-pressed to find one whose fluid isn't black or at least brown. In my opinion, most automakers (Ford included) aren't concerned about having your car make it to 300k miles or more - thus, there hasn't been a big push to mandate more frequent tranny fluid change intervals. Their thinking is that a car can go 150k without changing the tranny fluid (but probably not much longer). This contrasts with motor oil, which if you leave it in an engine for more than 15k miles or so, it's going to cause damage. It's the same deal with things like brake fluid changes - the manual doesn't specify it, but if you're aiming for maximum longevity, it's something that should still be done routinely.
Again, I appreciate the research that you've put into your posts. I suppose I do err on the side of caution when it comes to transmission fluid. But again, given that the Mercon LV is synthetic, and costs about the same as Amsoil or Mobil 1, why would you want to change to a non-OEM brand?