A beautiful page to clear up some myths and answer some questions on E85.
Usually false. Let's look at some current prices locally which are usually consistent from each other. First of all 30% is a pretty high amount, usually running pump E it's a 20-25% margin, but let's use 30 for fun and a 15gal amount.
93 Premium @ 3.39/gal and E85 @ 1.69/gal
Premium - 15gal = $50.85
E85 +30% more is 19.5gal = $32.96
So based on that above it is still cheaper even buying more. Yes, you will burn more and you are not increasing your tank size which means less MPG's and you will be at the gas station a little more often, but with a boosted car where E85 gives you safety and more power isn't it worth it?