Originally Posted by AZfocus2012
It is a high compression engine 12:1, and high compression engines need higher octane fuel. I believe in Europe cars are required to be able to run on 87 due to high fuel prices. So Ford works the ECU and cam timing to make it run on 87. Doesn't mean it will run well. In reality, this is a premium only car, capable of running on 87. Most on here experience an increase in MPG that offsets the added cost of running premium, and in most cases cost less per mile.
This is one of the intended benefits of direct fuel injection: the evaporation of fuel directly injected into the combustion chamber cools the charge sufficiently to allow use of lower-octane gas in a high-compression engine. A 12:1 compression ratio engine would not work well or long with conventional port injection.
For what it's worth, I have noticed no real driveability/economy difference between premium and regular.