At least in Ohio there is no E0. It's all E10. With some tunes (like Stratified) you can buy a single file combo tune that lets you switch from E30 to 93 or 91 while driving using the cruise control buttons. It is instantaneous and very slick. There are up to 5 "slots" in a file. I have 93, E30, 93 eco (15 psi boost limit), E30 eco, and valet (3000 rpm limit). All selectable on the go.