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.
I live in Hampton Roads VA (SE) I have to drive out to the more rural areas (farm country) to buy Ethanol Free. I know that my small 4 stroke engines loves it. One pull and it’s off to the races. I have a 2019 F150 , I need to run it down to a quarter tank or less before I add the Ethanol Free.
I use 100% gas gas for my small engine equipment. It’s quite pricey. Easily 25% more than the standard grade (87 w/ ethanol). If you get into the 93octane no-alcohol fuel look to pay 30% higher prices. Ergo the efficiency becomes a math question. Do you get an equal percentage gain in mileage compared to what you’re paying extra at the pump?
I had a Mercury w/ one of those 100k mile-tune-up engines, and the deal was you had to run premium and use synthetic oil for the oil changes… which I did (regular premium, 10% ethanol added), and I’ll be damned if I didn’t get 100k flawless miles out of that engine. Not a single hiccup.
Miles per dollar is lower. I haven’t done the arithmetic to tell you exactly how much. For me, it is more about denying Washington state money. I buy a higher percentage of my gas in Idaho, and when I do buy gas in Washington, I need fewer gallons.
I live in Spokane. I wait until at least a quarter tank left then head for the Costco in Coeur d’Alene. A few times, it was a buck a gallon less. No small thing with a 31 gallon tank. But, denying tax revenue to Washington is as much a reason to drive to Idaho as the savings. Do NOT feed the machine that would just as soon see you dead or gone. I haven’t tried premium or ethanol-free in my truck. I guess I should try it at least once.
Here in NW Wyoming gasoline prices are quite high, since it all has to be trucked in from the nearest refinery. If we drive over into Big City™ in Montana it’s significantly less expensive.
The premium gasoline here is uniformly (at every station) 91 octane ethanol-free. I learned a long time ago that ethanol-free premium was the only thing to run in small engines like snowblowers, chain saws, and lawn mower since it didn’t gunk up the carburetors nearly as quickly. I always have a couple of mil-surp 5 gallon cans filled with ethanol-free premium, treated with SeaFoam and Stabil; they get cycled through the truck about every 3 months.
I’ve found that whether it’s mountain driving or basin driving I get better mileage with the premium gas; I track it pretty carefully and it’s about a 10% improvement over “regular” (which is either 87 or 88 octane around here). My truck is a 2020 Toyota Tundra with the 5.7L V-8 4WD, and I’ve gotten as high as 25 MPG when driving through mountains at 55 MPH or slower (the speed limit in Yellowstone is 45 MPH). As long as you shut off the engine when you run into a buffalo- or bear-jam you can get great mileage there. Making grocery runs into town results in much lower mileage, around 17 MPG.
So as long as the price of ethanol-free premium is less than 10% more than regular, it makes economic sense to put that in our vehicles. But even when gas prices are low and premium starts running 15% higher, I still use it because I don’t want to personally subsidize the lobbying industry in D.C., or the giant agri-business industries that have fought so hard to use taxpayer dollars to grow more corn and turn it into economically-unviable and environmentally-destructive “fuel”.
Hard to find it around here but when I am in PNW, it is pretty easy as people need it because ethanol eats boat engines and lots of people have them. Ethanol is less energy dense than gasoline so it doesn’t surprise me that mileage is better. I would suggest that 604 miles on an empty tank is probably a sensor failure, though.
It was 609 after filling up. 608 by the time I took the picture.
I routinely see a reported 500+ range on a full tank. With slow speed driving (lower windage losses) to and from our destination, the short-term MPG went up high enough to give me an abnormally high range estimate.
I live in southern NH — have never seen ethanol-free gas anywhere, didn’t even know it existed. (Well, perhaps Avgas is ethanol free, that would make some sense — but I don’t suppose you could get that put into a car…)
Interestingly enough, a friend of ours owned a Cessna 152 for which he got paperwork to allow it to be filled with automotive gasoline. I don’t think it even required any changes to the plane, just paperwork. And a fuel container for his van to carry the fuel to the plane. It was worth the work given how much cheaper the fuel was.
Re ethanol lobbies: yes, and they are trying to force more than 10% ethanol, in spite of the fact that car manufacturers all say the warranty is void if you use that (apart from the few US cars that handle E85 fuel as a sop to politicians).
Some years ago, I had the opportunity to round-trip on a fairly regular basis to somewhere with ethanol-free gas. It was far enough to mostly empty my tank but not require filling up along the way. I would drive there, fill up with real gas, and drive home.
This was a very nice experiment. It wasn’t perfect, of course (ideally, I would try it the other way around half the time to eliminate things like “which side is higher elevation” and such), but it was better than most people will ever have a chance to do *just as they go through life*. Amazingly convenient.
Result: If I could, I would happily pay for the gasoline, full price, and give the ethanol back for free. I got slightly better than 10% better gas mileage with the pure gas than with the gasoline contaminated with ethanol.
And yes, “contaminated” is the right word. In my experience, it is a LOSS.
I’m gonna start asking people: Would you replace 10% of the gas in your tank with moonshine? No? Why not?
I’m not a mechanic or a physicist, but from what I understand, ethanol burns just fine, but we don’t use gasoline in our cars because “it burns.” Wood burns, sawdust burns quickly, but you don’t put sawdust in your fuel tank (unless you WANT problems).
No, we use gasoline because with the right fuel-to-air ratios, it EXPLODES. It’s that harnessed explosion that drives the pistons of your engines.
Ethanol … doesn’t explode, not to the same degree that gasoline does.
The engine’s sensors and regulators measure real-time (every few seconds, maybe up to a minute) fuel consumption — when they detect less fuel required to maintain a given RPM level, they report significantly higher ranges and fuel economy.
When it explodes, the combustion cycle is very wrong. That creates what you hear as a knock. It is very damaging. The ECM has knock sensors and will adjust timing and boost pressure to avoid knock. High octane fuel allows higher pressures without knock. Hence, the timing can be advanced, and you can get a more efficient combustion pressure cycle. The combustion cycle is a rapid burn. Just like smokeless powder in modern cartridges. You want it to burn and generate a pressure curve that can be contained while the bullet accelerates down the barrel. A detonation “disassembles” the chamber before the bullet leaves the barrel.
Nitroglcycin will also burn or detonate. Most dynamite can be safely burned without an explosion.
Ethanol has a different ratio of H, C, and O atoms than gasoline. The energy produced in the combustion of a gallon of ethanol is less than per gallon of gasoline. Mixing ethanol with gasoline dilutes the energy per gallon compared to pure gasoline.
Ethanol is also more corrosive than gasoline and does not store as well.
It’s close enough to an explosion that the human eye can’t (or can *barely*) tell the difference. It’s one of the technical differences that *does* matter… but only for very technical things.
Odd how the proponents of bastardized gasoline never mention how ethanol produces over a third less BTU per gallon than standard gasoline blends whilst weighing a bit more. Only a commie would call this a win.
From about ’99 to near covid days, I drove a ’91 Eagle Talon AWD/turbo stick. I quickly learned that, to run properly, it required the best gasoline I could find. That was Chevron 91 (bay area of CA). I occasionally tried other brands, sometimes due to availability on trips. This was a high performance engine with an early management system. Mostly it fiddled with the engine knock detector that killed the spark advance system. It ran terrible on anything with alcohol content. Hard starting, rough running, bad idle and poor throttle response, and really bad fuel mileage. Literally, the only gas it ran well on was Chevron. I see that some of the gas brands have reworked their formulas recently, so this data may be out of date to some extent. I suspect that better engine management systems may hide less than ideal fuel in newer cars now.
That was a neat, good handling car, with the potential to generate big HP gains with modest money investments. Easy to get 400 to 800 hp at the wheels for a street car. I never had the money to play with it, sigh…