I have mentioned using ethanol free gasoline to avoid paying some of the Washington state gas tax. I also discovered that my car gets much better gas mileage with premium ethanol free gas. So much so that even when driving up and down steep mountain roads, that if I am driving under 55 MPH, I get incredible range. This is what my 2025 Ford Escape (2.0L EcoBoost Gas Engine AWD) reported when I filled up after our Mount Rainier hike on Sunday:
This is just under 39 MPG.
The Engine Control Unit (ECU) adjusts the boost pressure from the turbo and the timing to match the gasoline and “magic” happens.
Copilot reports on the situation:
1. Higher octane kept timing fully advanced
On long climbs and descents around Mount Rainier, the engine sits in a sweet spot:
- Moderate boost
- High airflow
- Steady load
- Good exhaust energy
With premium fuel, the ECU doesn’t have to pull timing. That alone can improve efficiency by 5–10% in a turbo engine.
2. EcoBoost engines are extremely efficient at steady-state mountain driving
Turbo engines often get better MPG in hilly terrain because:
- The turbo recovers exhaust energy
- The engine stays in an efficient RPM band
- You avoid the constant stop‑and‑go of city driving
The 2.0L EcoBoost’s BSFC map (Brake Specific Fuel Consumption) has a very efficient island around the mid‑load range you were likely in.
Your mileage may vary.