Best brand of gasoline?

This is an old thread, but I'll use it rather than start a new thread. I'm in Utah where the gas is 85 87 or 91 octane. I fueled up with 88 octane to get ethanol free to try it. On the freeway at 80 mph I achieved almost 54 mpg. The best I did before that was around 45mpg. That is a 17% increase which is what prompted me to find this chat to see what others have said about it. (2026 LE AWD) According to dollars, I was only getting a 13% difference in gas price so it doesn't quite make it cost effective to put the 88 octane in. UNLESS I am going on long trips between pumps. And yes, that is a thing here in the west, especially when going through Nevada. You can stop at the little gas spots, but expect to pay much more for "convenience" gas.
On a side note: last year I drove a lonely highway through Nevada at 100 mph in my Infiniti and went a full 20 minutes before another car went by in the opposite direction. Don't stop though, the government did hundreds of nuclear tests in Nevada.

 

That's a big change that you are attributing to the lack of 10% ethanol.
Do you happen to know the wind speed and direction that particular day? A 20 mph direct tailwind could be the cause....

I have a different 88 Octane story: We were coming home from 3 days camping in the Ozarks in our new to us RV based on a Transit van.
I bought 15% ethanol, 88 Oct gas for $2.52/gal, which was cheaper than the normal 87 Oct w/ 10%.
It had a placard claiming 'It's fine for 2001 and later'....
30 miles into that tank the engine started bucking and popping and loosing power. It was flashing the CEL. I pulled over. It stayed running.
The CEL went out. We continued and it didn't act up again. I haven't checked to see if it stored fault codes.
I'm guessing a small gulp of water came along with this gas.
Next town I filled it up with No Alcohol 90 Oct for max dollars.... It only took 4 gallons, but I personally felt better.

 

I did have the wind to my back on that trip, but even with wind before I couldn't achieve gas mileage into the 50's at that speed. You are correct though. Two things that will kill mileage in a Prius are wind and speed. Same for every vehicle, I guess, unless they have a lot of horsepower. They will still lose some gas mileage, but not to the percentage extent of a Prius. Hills also, but you can regain mileage on the downside.
And yes, it sounds like some water in the gas for your issue. Did you put Heat in the tank, or just refill? I don't know if condensation in the tank will be an issue or not this winter. I don't know much about the tank in Prius models compared to the older vehicles. I usually keep my tanks above 1/2 full at all times in the colder months.
Prior to this chat, I didn't know ethanol free stores longer. I'll be using that in my 4-wheeler now because it is only used as a snow plow.

 

Alcohol in gas absorbs water into solution, that’s the best part of using it. Straight gas is where the engine could get a gulp of water. Heet is a type of alcohol.

 

Carburetor based small engines can be damaged with stored gas with or without alcohol. Most fuel stabilizers don't work great but Sta-Bil is worth using.

Even with a good stabilizer it's best to run the carbureted engine dry, add stabilized fuel and run it for a few minutes.

 

Yep; suppose to put in above 87 octane gas. The ECU should compensate for lower or higher grade gasoline. But expect less power and worse mpg - due to lower energy content of the fuel.
Toyota Prius - Fuel information - Specifications

 

Wroing'O, Buck'O.
Gasoline has a fixed energy content, BTU's per gallon.
Octane ratings are after additives are added to help with detonation/Preignition. Look it up.

Alcohol has less BTU/Gal, so that's why there is less energy in '10% ethanol Gasoline'.

 

Don't know what hairs your trying to split here?? I didn't write the supporting document.

You seem to have contradicted yourself, since most gasoline is mixed with alcohol - unless you can find a gas station that sells gasoline without alcohol mixed in.
Are you trying to say that there's no performance difference in 87 octane gasoline mixed with alcohol vs no alcohol????

 

No.
You said "energy content" ....

And I said, "Gasoline has a fixed energy content, BTU's per gallon.
Octane ratings are after additives are added to help with detonation/Preignition."

Octane has nothing to do with the BTU's of the gasoline.
Of course Gas with 10% alcohol has less BTU's per gallon than Gas with No Alcohol.

So theoretically gas with 10% alcohol will 'perform' less than 'no alcohol gas'.
Maybe this shows up in accurate MPG tests.

And theoretically a car designed to take advantage of high octane gas will 'perform' better than on low octane gas.
Maybe this shows up in acceleration times.

That's all....

 

A Prius will take advantage of higher octane in performance or mpg through timing changes enabled by the knock sensor.

From a consumer economics standpoint, no ethanol 88 octane has a higher octane coming out of the refinery than the gas used in e10. Therefore no ethanol gas is more expensive per gallon than 88 octane e10. Both perform the same.

Today's Central Texas Pricing at QT

 

Returning from UT-CO ski trips, my Subarus and now RAV4 have often achieved eyepopping MPGs going northbound on I-15 through the Salt Lake area. There's gotta be some good tailwind. Some natural, but some created by adjacent traffic.

85-86 octane gasolines are sold only at higher altitudes (with no nearby low elevation areas), where air is less dense and lower pressure, thus reducing air drag, reducing engine "pumping" loss in traditional engines (not maybe not hybrid engines), and reducing octane needs. At these elevations, I do get less power, but MPG increases, regardless of octane level.

As Bill partially noted, energy content is not strongly linked to octane level. According to my sibling who actually controlled gasoline blending in a major refinery for some years before moving up, the lower octanes produced at their refinery usually had slightly higher energy densities than the higher octanes. (That was back before the year-round ethanol mandates, I don't know what process and blending changes have happened since.)

 

Do you normally use the high elevation 85 regular? If so, the higher octane alone could provide some improvement.

Most ethanol free gas is nonoxygentated. Long term use will lead to more deposits forming in the engine.

Or the higher ethanol content loosened up some of the gunk that had built up in the fuel system. That is an issue for older cars and equipment when switching to an ethanol blend for the first time.

There is no single gasoline molecule; it is a mix of compounds that vary with the petroleum feed, refinery, season, and EPA region. The energy content of summer and winter blends vary as much as that of E0 and E10. The non-alcohol octane boosters tend to lower the energy content of high octane fuel compared to regular. High octane engines are just more thermally efficient when using them.

Might also have a general decline in that direction.

 

I don't believe the Great Salt Lake has much tilt. The Interstate is not much above the lake, for a quite considerable distance.

 

Yep this video changed my perspective on leaving gas in my small engines and gas cans. Now, I make sure NO gas is older than 6-months in anything.

When I put my small engines away for the season, I just drain the gas out and then run the engine until it dies to get everything out of there. (I have had clogged/dirty carbs in smaller engines...never fun to clean them out.)