http://www.youtube.com/watch?v=90szKQAjhfo
SO, I have a Bronco, and it's sole purpose in life is to please me and do my bidding. I don't plan to ever baby it. I've already got a baseline MPG for the truck and the ONLY thing I have done to the powertrain since then is install new rear axles (Old ones were not worn) and wheel bearings. I will test this acetone theory myself in a couple of weeks (During hunting season, thus, lots of driving to the hunting land and such)... just for sh!ts and giggles.
How about an MSD Ignition system? I will also be installing one on my K2500 while I'm on vacation, so I will post any MPG changes that I receive.
I have only ever gained substantial mpg gains with tune-ups, narrower tires, or hotter ignition systems. What is your spark plug gap at the moment? How old is your diff oils?