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Discussion Starter · #1 ·
Between June 15th and August 3rd, covering some 5,979 miles, I was able to compare the difference between using 87 octane pure gas with 87 octane with 10% ethanol. This experiment covered 14 fill ups, 7 with pure gas and 7 with the 10% ethanol. I made sure to exclude the first time I used pure gas and the time I switched it up to 10% ethanol to make sure my fuel tank was filled as close as it could be without having mixed fuel. I did my best to ensure the driving conditions were the same for both types of fuel which ended up being roughly 70% Highway / 30% City, all driven in Eco mode. The only true variable was the weather with the 10% ethanol test perhaps being done in a little bit warmer weather. I tried to use my air conditioner at the same setting regardless of the outside air temperature. Throughout the course of the experiment, the pure gas cost $.05 per gallon more than the 10% ethanol gas. I was running this experiment to see a) if I would get better MPGs with the pure gas and b) if it made economic sense to switch to using pure gas. Here are the results:

With pure gas, I averaged 44.1MPG.

With the 10% ethanol, I averaged 40.5MPG.

I estimate that I will drive 33,800 miles/year, which equates out to a savings of $152/year. That doesn't seem like much, but it is a monthly cell phone or cable bill in savings.

So there you go. If you're curious where you can buy gas without any ethanol, you can check it out here:
 
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Looks like roughly less than 10% better. So if pure gas is more than 10%, you do better using 10% ethanol. That is the case in my area.
 

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Unfortunately around here in WI the pure gas that can be easily found is only Premium. At approximately 0.80 more than regular, it’s not worth it.
 

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Between June 15th and August 3rd, covering some 5,979 miles, I was able to compare the difference between using 87 octane pure gas with 87 octane with 10% ethanol. This experiment covered 14 fill ups, 7 with pure gas and 7 with the 10% ethanol. I made sure to exclude the first time I used pure gas and the time I switched it up to 10% ethanol to make sure my fuel tank was filled as close as it could be without having mixed fuel. I did my best to ensure the driving conditions were the same for both types of fuel which ended up being roughly 70% Highway / 30% City, all driven in Eco mode. The only true variable was the weather with the 10% ethanol test perhaps being done in a little bit warmer weather. I tried to use my air conditioner at the same setting regardless of the outside air temperature. Throughout the course of the experiment, the pure gas cost $.05 per gallon more than the 10% ethanol gas. I was running this experiment to see a) if I would get better MPGs with the pure gas and b) if it made economic sense to switch to using pure gas. Here are the results:

With pure gas, I averaged 44.1MPG.

With the 10% ethanol, I averaged 40.5MPG.

I estimate that I will drive 33,800 miles/year, which equates out to a savings of $152/year. That doesn't seem like much, but it is a monthly cell phone or cable bill in savings.

So there you go. If you're curious where you can buy gas without any ethanol, you can check it out here:
Good stuff and it fits with my experience. That said, finding “pure” gas in the Midwest is really tough duty. Ethanol is a real political issue and, because of that, we are forced to pay even more into the subsidies for the farm industry.
 

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Just looking at BTUs available in a gallon of gas, pure gas has 3% more. Which should translate to 3% better mpg. Your test indicates much better performance than that.
 

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Just looking at BTUs available in a gallon of gas, pure gas has 3% more. Which should translate to 3% better mpg. Your test indicates much better performance than that.
How much is used doesnt quite work that way. The volume of gas shot in the cylinder each time has to do with how much oxygen is mixed with the fuel and since ethanol has an oxygen molecule in it then it actually adds to the oxygen in the cylinder. This is why drag cars used alcohol, even though it has less energy per volume the chemical makeup makes sure that you inject more of it into the cylinder for each bang cycle.

A very simplistic representation of the chemical equation is

Carbon/Hydrogen Compounds + Oxygen ---burns to give---> Carbon/Oxygen Compounds + Hydrogen/Oxygen Compounds
 

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Discussion Starter · #7 · (Edited)
Looks like roughly less than 10% better. So if pure gas is more than 10%, you do better using 10% ethanol. That is the case in my area.
So based on my numbers, pure gas is a 8.9% increase in fuel economy for a 1.8% increase in price per gallon...
 

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Around here, its illegal to sell pure gas to cars. 10% Ethanol is mandated year round.
 

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90% gasoline gets you 90% of the miles, so ethanol is just water? BTW, my previous experience is that the ethanol blend causes a 10% drop in MPG.
 

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The energetic value of Ethanol is much lower. In my C-HR hybrid i did a few tanks with E10 (RON95); milage drops immediatly with 5-15% depending on weather and landscape.
In my RAV4 it doesn't work either; less power, much higher consumption under the same conditions. I did measure it, so it's not completely subjective.
First graphic below: The long term fuel consumption of my previous C-HR; in the green the E10 RON95 fill-ups. Blue line is l/100km; the purple line is km/l.
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Graphic below: Fuel efficiency of my 2019 RAV4 hybrid. Again, the green area's represent the fuel consumption with the E10 RON95 tanks.
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I'm avoiding the use of E10, but over here in NL the governement decided to replace all E5 (RON95) with E10 in the coming years. I will refuel in Germany (E5, RON98). With that fuel it runs the best.
 

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Discussion Starter · #13 ·
Awesome info, VonJot! Your numbers validate what I observed...
 

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Discussion Starter · #14 ·
FWIW, the U.S. Government says you should only see a 3-4% decrease in MPG using E10...
 

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FWIW, the U.S. Government says you should only see a 3-4% decrease in MPG using E10...
Across the board that might be pretty accurate. My 2007 Tacoma saw about a 1MPG drop with E10, which was ~5%.
 

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When Oregon mandated 10% ethanol gas the mileage on my then 2000 Hyundai Elantra dropped from 38-40 mpg highway to 32-33 mpg. Great fuel tax grab for the state with the increased mph fuel consumption. Had a running email debate with the EPA about the decline and they blamed it upon the alleged lack of maintenance about my vehicle even thought it had been maintained per Hyundai published specs.
 
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When Oregon mandated 10% ethanol gas the mileage on my then 2000 Hundai Elantra dropped from 38-40 mpg highway to 32-333 mpg. Great fuel tax grap for the state with the increased mph fuel consumption. Had a running email debate with the EPA about the decline and they blamed it upon the alleged lack of maintenance about my vehicle even thought it had been maintained per Hyundai published specs.
Unfortunately some cars were never designed to have 10% ethanol in them and they aren't optimized very well for it. Some cars even had major problems with it because the rubber parts were never made with the intention of being in contact with ethanol. Politicians didn't care and/or are too stupid to realize the problems it would cause
 

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Unfortunately some cars were never designed to have 10% ethanol in them and they aren't optimized very well for it. Some cars even had major problems with it because the rubber parts were never made with the intention of being in contact with ethanol. Politicians didn't care and/or are too stupid to realize the problems it would cause
It’s the farm lobby pushing all this who could care less what this does to our vehicles. As long as they (and the politicians who do their bidding) get their pockets full, they’re happy.
I’m fine with the idea but the implementation sucks. They should make it so it’s got the same power/mpg characteristics as pure gas.
 

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They should make it so it’s got the same power/mpg characteristics as pure gas.
Can't really do that, you are limited by the chemistry there.

When I was a kid growing up in the late 80's/early 90s in West Virginia I remember Go Mart's pumps had a statement that said it contained up to 10% ethanol. I have to wonder how long the midwest area has had ethanol in its gas. I was a bit confused by all the people where I live now suddenly having problems with small gasoline engines because of ethanol because as far as I remember it had been in the gas I used to mow yards with.
 

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Can't really do that, you are limited by the chemistry there.

When I was a kid growing up in the late 80's/early 90s in West Virginia I remember Go Mart's pumps had a statement that said it contained up to 10% ethanol. I have to wonder how long the midwest area has had ethanol in its gas. I was a bit confused by all the people where I live now suddenly having problems with small gasoline engines because of ethanol because as far as I remember it had been in the gas I used to mow yards with.
I realize it’s a chemistry issue but would hope for a breakthrough with a more advanced chemistry or an improved refining process control recipe. I was gone from the Midwest for over a decade and ethanol was here when I came back.
 
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