In the winter I believe it's e70. And who knows when they switch over. Plus I've read it's not the best to keep in your car when in storage(although I'm not sure that will apply to all fuel system setups). In the end I prefer to KNOW what is in my tank. $400 to know vs. getting the wrong stuff and your engine going boom if you run your e85 tune on 93 or worse 87. Worth it IMO.