It's selling for an average of $3.41 / per gal in CA vs avg of $4.07 for E10. About a 18% difference. So the question becomes, what's the mileage hit on E85? From fueleconomy.gov " FFVs typically get about 25-30% fewer miles per gallon when fueled with E85." Let's see...18% fuel cost savings vs. 25% hit in mileage. Which one costs more? PS: That retail price spread has varied between 10% and 18% over the last year according to E85prices.com and averages about 16%.