We have a few gas stations nearby that sell mid grade (89 octane) for the same price as regular 87 octane, and it has got me to wondering how they can do that, and why anyone would buy the regular?

I have wondered how ethanol content effects octane rating?
I currently purchase premium (93 octane) pure gas with no ethanol from the same station for my SS. On long trips where I have to refuel on the road, I still run 93 octane, but notice that sometimes my fuel mileage suffers.

In my LT1 (2.2), I run regular 87 octane, but notice that I get better mileage from some stations than others on long trips. (It's not just the wind/direction)

I know that ethanol is not as efficient as gas as far as fuel mileage goes, so I am wondering if ethanol increase the octane rating?

 

I would doubt that mid grade would be the only ethanol grade since there is no separate tank for mid grade it is just a blend of regular and premium. I don't know what if any affect a little ethanol will have on gas but I was told that E85 is 105 octane.

 

Yes, ethanol is used to INCREASE octane ratings.

I noticed this primarily in the northern states....Dakotas for example. The pumps there listed several different octane ratings. And expressly indicated the upper level gas was enhanced with ethanol. They also gave one or 2 grades of gas in "non blended". Ethanol enhanced grades was slightly less in cost, if I remember correctly (I think Sinclair was the predominant brand).

 

I am not saying that mid grade is the only grade that they add ethanol, I mentioned that when I travel I fill up with premium at other stations on occasion. I notice a drop in mileage sometimes, and wondered if maybe these had ethanol vs my pure gas?

Also, Are you sure that ALL stations mix to get mid grade? I thought only some did that? I just wonder why my local station sells mid grade 89oct at the same price as regular 87oct? Could the mid grade have more ethanol and thus boost octane rating?

If E85 has an octane rating of 105, that may be my answer... Yes, ethanol increases octane rating, but not necessarily MPG or performance?

I'm just trying to learn.

Come on, I know there are some real scientists out there.....

 

I thought I answered your question as you asked it.
"I know that ethanol is not as efficient as gas as far as fuel mileage goes, so I am wondering if ethanol increase the octane rating?"

If this is a new question, "Also, Are you sure that ALL stations mix to get mid grade?"....no I am NOT sure. But it COULD/WOULD be a cheap way, except it may increase the percentage of ethanol in the mixture.

 

There is a gas station up by my trailer that sells 89 for the same as 87. Everytime I get the 89 in any of my vehicles I get a check engine light. I thought it was just a fluke the first time, but I have tried with our other cars and get the same result. Nobody that lives out there has had the same problem, but I am using the Chicago blend of gas 95% of the time so maybe it is the switch to the rural gas that causes it. Long story short I just get the regular 87 or the premium 92 to avoid this problem.


SPPD

 

Snoopy, sorry about that I should have quoted nss79 as I was replying to his message at the same time you were posting your response....

 

I noticed while on vacation that when I use the gas with ethanol I didnt get as good of mileage as regular gas.

 

.5%-1.0% drop in fuel economy, which can be made up by using cleveandhhr's driving techniques.

 

Most of central Florida stations all sell gas with "up to" 10% ethanol blended gas and it is for all grades. I'm using 87 octane and my mileage has dropped about 10% since the push for the blending of ethanol. I shouldn't complain as I'm still getting ~30 mpg, but I had been getting 33-36 mpg on the highway when the car was new in '06.