It gets worse. Ethanol is a solvent that can loosen the sludge, varnish and dirt that accumulate in a fuel tank. That mixture can clog fuel lines and block carburetor jets.Blame the Renewable Fuel Standard. This government-mandated rule requires certain amounts of ethanol and other biofuels be blended with gasoline and diesel fuel. But when Congress first passed RFS as part of the Energy Policy Act in 2005, our demand for energy was increasing. Today, it’s the opposite. Total demand for fuel has decreased thanks to more-efficient vehicles, more hybrids and increased environmental awareness. The EPA is set to release the 2015 standard in June. Meanwhile, some legislators are pushing to reform or eliminate the Renewable Fuel Standard entirely.