On my "test drive" (I had already bought the car), the salesman and I stopped at a gas station to fill up the gas tank and I had to stop him from filling it with 87 octane regular. He mentioned that the car will run on 87 but I mentioned the part about it losing 20 HP when you do that. I convinced him to fill it with 91 but now that I think about it, I should not have had to. With a car that has a small a gas tank, the difference between regular and premium is three or four bucks and its a performance car, it doesn't need to get hobbled by cheap gas right out of the gate. If anyone from Ford or a Ford dealership is reading this, get the new Ecoboost cars filled with premium so the first tank is a good one. If your customers want to cheap out later, that's up to them. As for mine, I'm going to keep it filled with 91 unless I can find better (I tried 5 gallons of Sunoco 96 at the race track).