It's my understanding that ethanol is added to gas at the point of wholesale distribution, i.e.; the tank truck driver calculates how much to add to his load. If so, this may explain the large variations found at the pumps. Add to that the fact that tanks at gas stations are never completely empty before they are refilled.

Understood, Ted. I worked in anti-counterfeiting for a decade. Fuels were our biggest money maker. It's funny, when we tested E85 blends for supplying a "green" research race, we kept getting E10, E15, or straight gas. Octane ratings were all over the place too. We finally called up a blender and had some E85 mixed up so the race contestants could actually get some real E85.
Anyway, our local counties have long failed to meet fresh air standards. So I guess ethanol is supposed to magically make up for folks idling in traffic for hours a day. Columbus, Ohio had a cool approach in the late '70s. Their main drags had synchronized stop lights. Once you got synced up, driving the speed limit would get you green lights for miles and miles. Dallas suburbs actually had the technology but city officials deliberately did not synchronize the lights because "We don't want people using our city streets as a main thoroughfare." Whatever.

You really do need to do a manual check for ethanol in the fuel to determine the real percentage content. It takes only ninety seconds to perform a check and the test can be performed with a homemade checker or one that is endorsed by the air craft industry. For Texas, most gasoline pumps simply say “May contain up to 10% ethanol” and that’s the generic disclaimer. Although I’ve come across as much as 30% ethanol at the pump, much of the time premium fuel does not exceed 5%. I’m still finding stations that have no ethanol in the premium although the other grades are pretty much consistent at the 10% levels. I'll add that ethanol does not like to be added to gasoline and as such, does not take much for it to separate.

Lorena, Texas (South of Waco)

IIRC there was something posted at some interwebz site stating that the whole ethanol thang has come under legal fire?

Avgas is an option, but how deep is your wallet? There is a new avgas called 82UL but that's dropping the octane a bit much for a street engine unless you build it with low compression. And that would be like hiring a hooker to just talk!!!

Dallas area is being forced to use E-10. I do not endorse that and do not subscribe to any real reduction in consumption nor pullution caused by the inclusion of ethanol.

Here’s the direct link to the Carb Shop article.

http://www.thecarburetorshop.com/Ethanoluse.htm

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I’ll add that premium fuel (91-93 octane) in my part of the country does not exceed 5% ethanol and with a little looking, I’m still finding premium without any ethanol. The 87 and 89 grades typically check out at 10%. That’s why I always recommend running premium fuel in any carbureted vehicles as it’s not for the octane but for the reduction in ethanol.

Lorena, Texas (South of Waco)

What follows is buried in the thread 'fuel line type' that Rono started. IMO, information pertaining to the modification of older carburetors for the use of ethanol fuels is worth posting as a separate thread subject.
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I haven't seen this info before...

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York