But here’s the other end of this story - a leaked Ford Motor Company document that was uploaded on the Mustang6g forum hints at a serious loss of oomph if you fill up with 87 octane gas, the regular gasoline rating for North America, Australia and New Zealand. Without further ado, the 2.3L loses 35 hp and 20 lb-ft (27 Nm) if you feed it 87 octane.
Another forum member puts the Mustang EcoBoost’s loss into perspective by comparing it with what happens to a Ford Focus ST when fed 87 instead of 93 octane gasoline. As it happens, “the Focus ST loses
All in all, do keep in mind the quality of the gasoline affects power ratings of any car, be it a 1-liter Fiesta hatchback or an EcoBoost Mustang. And truth be told, it’s redundant to buy and drive a made-for-thrills machine such as the sixth-generation of the iconic Mustang, then fill the tank up with regular octane, especially when a gallon of premium gas costs a lot less than it did last year.