The 2015 Ford Mustang Ecoboost is a very enticing package on paper. It produces 310 horsepower and 320 pound-feet of torque from its boosted four-banger, numbers that will leave a 3.7-liter V6 equipped Mustang in the boosted pony’s rearview, not to mention the added benefit of greater fuel economy thanks to the less thirsty four-cylinder.
All those benefits come with one requirement: that owners fill their Mustang EcoBoost with 93 octane, the pony’s preferred drink of choice according to the owner’s manual. Modern software tuning will allow the Mustang EcoBoost to run on lesser fuel, like 87 octane, but filling it up with lower grade fuel certainly isn’t the best move considering a new report on major power loss associated with the lower grade gasoline.
A vehicle optimized for 93 octane will loser power when filled with the cheap stuff. That’s a well-known fact of life in the automotive enthusiast community. But the power loss of the Mustang EcoBoost is pretty substantial. According to a Ford training manual located by Mustang 6G, the power of the 2.3-liter EcoBoost engine is dialed back to 275 horsepower and 300 pound-feet of torque — a power loss of about 11.3 percent compared to the power you’d find under the pedal when the Mustang EcoBoost is sipping premium fuel.
Mustang 6G says that the loss is actually not as bad as originally expected because, according to their sources, a Ford engineer previously quoted a 13 percent power loss while running lower grade fuel, but mentioned that peak torque would remain unaltered. Meanwhile, our friends at Autoblog reached to Ford for comment and were contacted by Paul Serednyski of Ford powertrain communications. He rejected the findings from the manual in question, although did not give specific numbers regarding Mustangs running on 87 octane. He did, however, say that “Torque remains unchanged” in respect to a Mustang EcoBoost running on 87 octane, and speculated that the manual in question was from a time before the 2.3-liter EcoBoost engine was certified, thereby showing incorrect numbers.
The moral of the story remains: for the best performance and fuel mileage, stick to93 octane in your Mustang EcoBoost. And though it’s certainly safe to use the temptingly-cheap 87 grade, the cheaper low-cost stuff will negatively impact peak power.