Highly recommend Ethos FR to everyone. You add this to the engine oil, transmission, power steering, differential, and fuel. Been testing it for about a month now and fuel economy increase 1.5 mpg. I didn't think that it would do anything when I added it to my oil since I use Amsoil exclusively and am a believer in it, but adding it to my oil increased the economy by 1 mpg. Nick Bird who is my contact and he asked me to try to get the word out on Ethos. I am sold on it and will be ordering more. Do a google on Ethos-FR and you will find their website. They would even treat your vehicle for free if you are in the Vancouver area. He might send you a free sample. I've been testing it with acetone and just recently with Xylene. Want to start using some Torco GP-7 for the PIB, and maybe some Coleman fuel too.
I don't think one additive will increase economy dramatically but a combination of additives. The hard part is finding the right combination.