Usual % of ethanol in E10 and E15 gas

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Is anyone aware of the average % of ethanol in E10 and E15 ethanol gas blends? Pumps here in PA are labeled with the "UP TO" 10 or 15% ethanol content. I imagine it's blended lower than the 10 or 15% max labeling to avoid any penalty when officials test it.
 
When covid hit I was getting incredible MPG on "regular" gas that was also about a buck and a half.

I think the alcohol was diverted to hand sanitizer.

Other than that, I bet I'm getting the full 10% every time.

You can test it yourself with a graduated beaker with a cork stopper. Put a measured amount of water in and shake it up-- whatever volume of water disappears into the gas is the percentage of alcohol.
 
It's very easy to test the fuel and get a pretty good idea of the ethanol content. I take 5 ounces of fuel and add 1 ounce of water, agitate the mixture and then let it sit for about 15 minutes. The alcohol will bond to the water and you'll see the separation from the fuel. Ten percent alcohol will make your mixture look like 1.5 ounces of water and 4.5 ounces of gasoline instead of your initial mixture of 5 ounces of gasoline and 1 ounce of water.

I routinely test the fuel that I buy for my lawn equipment to make sure it's ethanol free. You can see in these images that the alcohol falls out of suspension and bonds to the water making my 1 ounce of water appear to be 1.5 ounces. It's bubbly because I only let it sit about 45 seconds.
1 oz water.JPG
water alcohol mix.JPG
 
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Most of the base fuel sold for that would be CBOB of RBOB, which is designed to be mixed with 10% fuel ethanol to reach the designated AKI octane rating. There's also different California reformulated blends. It really doesn't make much sense to do otherwise. I guess it's possible though, but I'm not sure what incentive there would be to have some sort of custom fuel blend for something like 6.5% fuel ethanol.


Now there is one issue where fuel ethanol is supposed to be between 2-5% gasoline as a denaturant, just in case someone thinks it's a good idea to use it as a cheap way to make their own vodka. I've heard that some blend in something like 10.25% fuel ethanol to make E10 on the premise that it will result in a maximum of 10% ethanol since there's that little bit of gasoline.
 
Most of the base fuel sold for that would be CBOB of RBOB, which is designed to be mixed with 10% fuel ethanol to reach the designated AKI octane rating. There's also different California reformulated blends. It really doesn't make much sense to do otherwise. I guess it's possible though, but I'm not sure what incentive there would be to have some sort of custom fuel blend for something like 6.5% fuel ethanol.


Now there is one issue where fuel ethanol is supposed to be between 2-5% gasoline as a denaturant, just in case someone thinks it's a good idea to use it as a cheap way to make their own vodka. I've heard that some blend in something like 10.25% fuel ethanol to make E10 on the premise that it will result in a maximum of 10% ethanol since there's that little bit of gasoline.
The part about 2-5% gasoline being used as a denaturant is interesting. Maybe that explains why Michigan (and other states) have a sticker on the pump stating that the E85 only contains a maximum of 83% ethanol. The missing 2% is gasoline that comes with the ethanol.
 
Need to test it - simple as that. I've tested ours here in VA, it's always 10%. Our E85 is 85% as well.
 
We use to do an experiment in our Gen Chem II lab where our students would measure the ethanol content of gasoline by gas chromatography.

From 2015-2020, I was the one who would go and buy the gas most of the time, and I'd get a gallon of regular 87 from the Speedway station up the street(in Louisville, KY). I'd typically buy it on a Monday afternono and it would be looked at Tuesday-Friday of that week.

Of course student data has to be taken with a grain of salt, but when a few hundred students are doing the experiment trends tend to emerge and the average is likely a decent picture of the real number. I saw numbers as low as 6% and as high as 9%. There was no real pattern I remember from doing the experiment in September vs. February/March.
 
From a fuel drivers point of view, filling my tanker truck up at the rack. If I wanted to fill a 1,000 gallon pocket with E10 the loading system would pump in 100 gallons of ethanol, then switch over to 85 base gas for the remaining 900 gallons.

So 10%
 
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