http://www.forearthonline.com/greenfuel/index.html

"Ethos Fuel Reformulator

Ethos is a unique combination of high-quality, specially designed esters that uses only the elements of carbon, hydrogen and oxygen. Designed for use in all fossil fuels, it is an effective solution for the air pollution caused by internal combustion engines. Amazingly, everyone can personally benefit from this fantastic product because Ethos Fuel Reformulator significantly reduces fuel costs.
Environment
Reduces vehicle emissions by 30% or more. Moreover, Ethos is non-toxic, non-hazardous, free of carcinogens, and 99.99976% ash-less upon combustion.

Economy
When added to both the fuel tank and crank case, Ethos increases fuel economy by 7% to 19%, but the savings doesn't stop there. Reducing friction producing heat increases the longevity of your engine and this means less downtime and lower repair costs.

Performance
Dissolves gums and varnishes, lubricates upper cylinder components, and keeps the entire fuel system clean."

Quoted from product page of above web address.

Anybody ever hear(or used) of the stuff? I always get skeptical when increases in anything are listed in precentages.