Recently rented a Flex Fuel Chevy Suburban. Noticed after a couple hours of highway driving it had already bured thru 1/2 tank of gas. Did not take much more time to get tho close to E. "What a pig" I thought when spending 80 buks to fill up. After having the car a week, I noticed every since the 1st fill up, it got much better mileage. When returning the car to Enterprise, I mentioned what happened and they said sometimes when they fill up the cars customers return near empty, they use E85 because its cheaper. The problem is when they use E85 to save them so dough, it screws up the next renter's gas bill due to the worse economy.