Ford's EcoBoost engines are engineered to accept regular 87-octane gasoline, yet the full performance figures the automaker advertises only arrive with premium fuel rated at 91 octane or higher.
The difference comes down to how the engine's computer manages ignition timing based on what is in the tank.
How Ford's Octane Adjust Ratio Changes the Output
Ford equips its EcoBoost engines with an Octane Adjust Ratio strategy inside the engine control unit.
Rather than waiting for knock to occur, the system identifies the octane level of the fuel present in the tank.
When premium fuel is detected, the ECU advances ignition timing to extract more power and torque, which also benefits fuel economy and emissions.
With lower-octane fuel, the engine pulls timing back to prevent pre-ignition and knocking.
This is the mechanism that allows engines designed to perform best on premium to also run safely on regular.
Owners can switch between the two grades without concern for engine damage.
The trade-off is straightforward: less power, reduced responsiveness, and likely higher fuel consumption when running 87 octane.
The Bronco illustrates the gap clearly.
Its turbocharged 2.3-liter four-cylinder is rated at 275 horsepower and 315 pound-feet on regular fuel, rising to 300 hp and 325 lb-ft with premium.
The turbocharged 2.7-liter V6 follows the same pattern, moving from 315 hp and 410 lb-ft on 87 octane to 330 hp and 415 lb-ft on high-octane fuel.
Independent testing has quantified the difference.
In 2019, Car and Driver put a used Ford F-150 with the twin-turbocharged 3.5-liter EcoBoost V6 on a dyno.
On 87-octane fuel, the truck produced 360 hp and 463 lb-ft at the wheels. Switching to 93-octane raised output to 380 hp and 475 lb-ft.
The higher grade also cut the 0-60 mph time from 5.9 seconds to 5.3 seconds and trimmed the quarter-mile run from 14.5 seconds to 14.0 seconds.
The flexibility extends beyond EcoBoost.
The naturally aspirated 5.0-liter Coyote V8 in the Mustang will run on 87-octane, but reaching its quoted 480 hp and 415 lb-ft requires 91- or 93-octane fuel.
The supercharged 5.2-liter V8 in the F-150 Raptor R is different.
Its owner's manual specifies a minimum of 91 octane, consistent with an engine producing 720 hp and 640 lb-ft.
For EcoBoost owners, regular fuel remains a valid choice where premium is hard to find or the extra cost is unwanted.
Those seeking the advertised performance, however, will need to pay for the higher grade.
