Ford's EcoBoost Engines Don't Demand Premium Gas, But You Might Want To Use It Anyway
If you've been wondering how Ford's EcoBoost engines make max power on 87 octane, sorry to burst your bubble, but they don't. Sure, the manual for your F-150 with the EcoBoost 3.5 reads "Your vehicle operates on regular unleaded gasoline with a minimum pump (R+M)/2 octane rating of 87," but what the average user will probably focus on is the big blue box with the number 87 inside of it. It's easy to miss the fine print reading, "For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended."
Car and Driver tested an EcoBoost F-150 with both 87 and 93, and found that on 87, horsepower dropped from 380 to 360, resulting in a 0.6-second slower 0-60 time. The reason Ford can say your EcoBoost is designed around 87, yet premium is the only way the 2024 Mustang EcoBoost makes its full 315 hp, is thanks to the power of the asterisk.
Go to Ford's website right now and check out the Mustang EcoBoost Fastback, and the site will tell you that the 'Stang delivers 315 horsepower and 350 lb-ft of torque. Then click on the little citations next to those numbers, and you'll get a message that reads, "Horsepower and torque ratings based on premium fuel per SAE J1349® standard." After that, go to the owner's manual to find assurance that your Mustang EcoBoost's engine was designed to run on 87. At a glance, it feels like EcoBoost owners are being pulled in two directions, and forums are full of confusion on the matter.
Here's how the EcoBoost runs on 87 without getting explodey
Ford's EcoBoost can modify performance on the fly via its Octane Adjust Ratio, which, if you're used to old-school laggy turbos that need high-octane gas to avoid becoming grenades, is pretty miraculous. Thanks to careful control of ignition timing and boost levels, EcoBoosts can run on 87 without creating engine-harming knock.
Knock is when fuel ignites too early in the combustion chamber, creating a high-frequency pressure wave that sounds like a little firecracker going off. When the engine is experiencing severe knock, it sounds like distant popcorn popping or, as a repair shop owner might call it, cash register noises. Excessive knock can lead to a host of unpleasant side effects, from premature bushing and bearing wear to bent rods, broken pistons, and even cracked cylinder heads in extreme instances.
Higher octane levels reduce knock because they help fuel resist unintended detonation. This detonation resistance is essential for high-compression or forced-induction setups such as turbocharging and supercharging because the more pressure in a combustion chamber, the more likely the fuel will explode when it's not supposed to. That's why premium gas exists — it lets high-performance engines run at greater boost pressures and compression ratios without the threat of knock.
Clearing up the confusion
Even if you totally understand that Ford emphasizes that its EcoBoost engines can use 87, yet advertises numbers generated on premium, it might feel a little like someone telling you to meet up at 12:00, neglecting to tell you that means midnight. Will you laugh off the error when you get roused from bed in the middle of the night, or would you have preferred more up-front clarification?
The EcoBoost lineup doesn't need this kind of confusion. Thanks to the big power and torque these engines can generate, you'll find an EcoBoost in everything from your uncle's workhorse F-150 to the ex-John Cena-owned barely-driven GT supercar. Oh, how times have changed. We all accept turbos as the norm now. Remember when Jaguar XJ220 buyers demanded their money back because it had a twin-turbo V6 instead of a V12? Small turbo engines power everything now, and can propel F-150s to 60 in under 6 seconds on plain-Jane 87. Try that in your XJ220! No, scratch that, please, please don't actually put 87 in an XJ220.
Also, don't put 87 in EcoBoost Ford GTs or EcoBoost F-150 Raptors (Rapti?), which, just to add another hair-pulling wrinkle to this story, do require 91+ octane.
All of this could be easily fixed by changing the owner's manuals. Instead of writing, "your EcoBoost is designed to run on a minimum of 87 octane," the phrase could instead be, "your EcoBoost makes its max power on 93 octane, and those are the figures you hear in commercials, but the engine won't explode if you fill the tank with 87, GTs and F-150 Rapti excluded."
