Should I switch to premium fuel?

[TakeTheBlack]

Almost all gasoline sold in the U.S. contains 10% ethanol. Ethanol actually is higher octane than straight gasoline, which is why it’s used as a racing fuel.


That sounds like something wind related.

Oh yes. When I slowed down (again into
Strong headwind) below 75 it stopped.

Does premium have ethanol? I live in a suburb of St Louis (close enough for emission rules). Thank you for the information.

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[Mark S.]

Actually not really. It's used in racing fuel (assuming you are referring to NASCAR). I worked several years with fire and safety quite often at the fuel island. Chicago and Michigan actually used a tanker. The move to E-85 was a publicity move. They still burn about four gallons per mile...trust me when I say...the ethanol isn't impacting their 700-900hp motors. I spoke with a lot of engineers and engine tuners to pass my day...it's crazy the tricks of the trade. .

I guess I was imprecise. Racing fuels are typically blends with more ethanol than gasoline. I don’t think anyone runs pure ethanol.

 

[Mark S.]

Does premium have ethanol? I live in a suburb of St Louis (close enough for emission rules). Thank you for the information.

Yes, almost all premium fuel sold in the U.S. contains 10% ethanol. And you’re welcome!

I’m in the Metro-East area, BTW. We’re practically neighbors.

 

[TakeTheBlack]

Yes, almost all premium fuel sold in the U.S. contains 10% ethanol. And you’re welcome!

I’m in the Metro-East area, BTW. We’re practically neighbors.

Only diff is you pay twice my gas tax.

Apparently Missourians are entitled to an annual partial gas tax rebate. I need an accountant to figure it out (must keep all receipts from buying gas and then file with the state).

 

[DMEARC]

I’ve looked far and wide for data to back this claim without success. Do happen to have a link to any evidence? For engines that can burn regular or premium timing is retarded to reduce power demand, which concurrently reduces heat. Generally speaking, less power means less fuel burned.

Here‘s two tests:

https://www.sciencedirect.com/science/article/pii/S2352146516302629?ref=pdf_download&fr=RR-2&rr=71a71404be0881f3

https://newsroom.aaa.com/wp-content/uploads/2019/06/Premium-Fuel-Phase-II-Fact-Sheet-FINAL.pdf

One shows an increase in energy consumption as octane decreases (although that test was at WOT), and one shows a 7.1% increase in fuel economy using premium fuel in a Cadillac Escalade.

 

[13MikeH]

Yes, almost all premium fuel sold in the U.S. contains 10% ethanol. And you’re welcome!

I’m in the Metro-East area, BTW. We’re practically neighbors.

I actually searched for premium minus ethanol as it is harder on small engines....found one station within 40 miles that sold 93 octane with zero ethanol. Small independent station.

 

[bjbena]

I actually searched for premium minus ethanol as it is harder on small engines....found one station within 40 miles that sold 93 octane with zero ethanol. Small independent station.

Right now that gas is probably well over $5. Our gas here in Georgia is relatively cheap and premium ethanol free is a hair under $5/gallon.

 

[Mark S.]

Here‘s two tests:

One shows an increase in energy consumption as octane decreases (although that test was at WOT), and one shows a 7.1% increase in fuel economy using premium fuel in a Cadillac Escalade.

The first link includes this:

“It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+).”

We don’t have specially adapted engines, and no one is selling 100 octane at the pump.

The second link includes:

“Although drivers of vehicles that recommend, but do not require, premium gasoline are unlikely to see any benefit from using premium gasoline during typical city or highway driving, a combination of laboratory and on-road tests were performed to simulate extreme driving scenarios such as towing, hauling cargo and aggressive acceleration.”

This makes sense given the engine control algorithm that advances timing when using premium only applies at high power output. If you are burning regular, your engine is already hot and you demand high power (aggressive acceleration) timing can only be retarded so far. The only option at that point to protect the engine from detonation is to enrich the mixture, which means you are using more fuel. A richer mixture burns more slowly, effectively retarding the timing of peak cylinder pressure. This will lower operating temperature and power output.

But we’re still at the same place; under normal driving conditions using premium offers no better efficiency. Here’s an article from Car & Driver testing several different vehicles using premium and regular. This is strong evidence (to me) that you should save your money and use regular (min 87 octane) unless you need the extra power.

https://www.caranddriver.com/features/a28565486/honda-cr-v-vs-bmw-m5-ford-f-150-dodge-charger/

 

[wiyeti]

22,000 miles on my OB now. I was putting in premium just to get away from the ethanol. Now I'm putting in regular to save some money. No drop in mpg. Still getting bout 480-500 miles per tank depending on where I go.

 

[John2Names]

I’ve got 2,000 miles on my OBX and I get 24-26 mpg city. Sounds like you have a problem. Premium will be a waste of money. Do you leave the auto start/stop on. That really makes a large difference with mine.

 

[Akjr206]

I'm about 1100 miles into my Outer Banks and I've noticed that the MPG hasn't been what I expected at about a combined 21 or 22 MPG. I've had a healthy mix of both city and highway driving. On the highway alone, I get about 24-25 MPG. In the city, I get closer to 19 or 20. It's gotten as low as 16 or 17. I'm hoping there's not a mechanical issue, but I do know that Ford recommends using fuel with higher octane.

I did some calculations— based on a combined 22 MPG on regular fuel, gas prices in my area, and my yearly mileage, I would need to get at least 24.5 MPG combined in order to "break even" and make buying premium fuel financially worth it. Anything lower than that would provide marginal MPG that is too low to justify the extra cost. If anyone wants my spreadsheet on how I calculated this feel free to let me know.

For those who use premium fuel, have you noticed an improvement in MPG compared to regular? Thanks!

Edit: forgot to add that I try to use Eco mode as much as possible and have auto-start/stop turned on.

Hi!
On highway I’m getting 31.9 mpg. Neighborhood cruising, it drops to 27-28.7 mpg, regular mode on the Badlands.

Guess it depends how we step on the pedal.

 

[cxp]

How hot is it? Is it 90 or above? Do you rev out the BS? By that I mean are you at 3500 or above RPM?

If you have heat, sit in stop and go traffic, and/or like to get on the throttle and ride the RPMs up Premium is worth it. Premium gives you better knock resistance and results in less timing cut during high rpm / boost. This is a standard with Ecoboost engines across the board.

You really feel a difference in the heat. If you put standard in, wait at a stop light and let the small intercooler heat soak, then get on the throttle with 87 octane there will be significant loss in power (occurs higher up in power band) and change in how the BS feels. This is a broad problem with turbo cars (small turbos) combined with small intercoolers. Heat = knock, more octane = less knock = more power / flatter torque curve.

If you drive more conservatively or don't care about getting maximum power or how the car feels as you accelerate than 87 is fine.

 

[zachc275]

How hot is it? Is it 90 or above? Do you rev out the BS? By that I mean are you at 3500 or above RPM?

If you have heat, sit in stop and go traffic, and/or like to get on the throttle and ride the RPMs up Premium is worth it. Premium gives you better knock resistance and results in less timing cut during high rpm / boost. This is a standard with Ecoboost engines across the board.

You really feel a difference in the heat. If you put standard in, wait at a stop light and let the small intercooler heat soak, then get on the throttle with 87 octane there will be significant loss in power (occurs higher up in power band) and change in how the BS feels. This is a broad problem with turbo cars (small turbos) combined with small intercoolers. Heat = knock, more octane = less knock = more power / flatter torque curve.

If you drive more conservatively or don't care about getting maximum power or how the car feels as you accelerate than 87 is fine.

Definitely dealing with high temps right now. I would say it’s a little bit stop/go because we don’t have too many lights, and I only find myself 3500+ RPM when I’m getting on the highway.

 

[cxp]

I only find myself 3500+ RPM when I’m getting on the highway.

Considering that high RPM is more occasional than regular for you I'd say 87 is probably fine. It's the top part of the torque and RPM curve where you will feel most of it.

If you feel hesitation or other weird things in the heat then you could try premium and see if the engine is more consistent. I'm guessing you're probably fine though on 87.

 

[Thelawgiver]

Use the Eco GOAT mode more often

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