Have you tried a bottle of dry gas?
I know my Ranger pickup gets 31 mpg with Chevron on the highway.As long as we're talking gas and additives maybe one of you all that know more that I can answer a question. I have heard from a few 'credible' sources that the only additive that does anything at all is Chevron Techron. All others are just snake oil (which might actually work...) Heck, I remember the days of Shell "Platformate" and it was the SUPER MILEAGE ADDITIVE!! So what say you on Techron?