Because research is still ongoing, a definitive federal ruling is at least a year off. But some drivers aren't waiting. In South Dakota this summer, gas stations were caught dispensing illegal E-30, prompting the Environmental Protection Agency to issue a terse warning letter to distributors. No doubt customers were attracted by ethanol's price tag—it was about 30 cents cheaper per gallon at several stations.
But there's a big trade-off. E-20, the October report found, gets about 7.7 percent lower fuel economy than straight gasoline.