http://www.epa.gov/MTBE/ its suppose to help oxygenate gasoline, but it has a lot more harmful effects than positive ones if you ask me... there's better oxygenators out there, I think because its economical and cheap to reproduce its become the standard (and now that people make a lot of money off producing it, they also lobby to make sure it keeps getting produced). The government would also lose a lot of tax revenue "The price of ethanol in most studies is assumed to be the market price, which includes the 54 cents per gallon Federal excise tax exemption. The addition of 100,000 barrels per day of ethanol to the gasoline pool would reduce Federal excise tax revenues by about $800 million per year.(5)" http://www.eia.doe.gov/emeu/steo/pub/special/mtbe.html