Couldn't remember when it happened, but in Fall 2013
"Iowa's largest pipeline operator, Magellan Midstream Partners, will no longer ship 87 octane regular gasoline to its Iowa terminals. Instead, the pipeline operator will start shipping 84 octane fuel, which can be blended with more expensive 91 octane fuel to produce the regular 87 octane product. Iowa requires a minimum 87 octane fuel at gas pumps.
The bad news for consumers is that the 87 regular octane fuel without ethanol will probably cost more — possibly a lot more — at the pump. The price for 91 octane premium gas without ethanol also could spike."
"Iowa and Nebraska are among the last states in the country to require a minimum octane of 87, he said, but shipping the 84 octane still allows for the product to be mixed with a higher octane product to reach the required 87".
https://qctimes.com/non-ethanol-gas-...ac35e8b14.html
I don't know if the same thing happened in most places, but the refiners made the choice I'm sure to maximize profits that 84 octane gas with 10% ethanol gets to the 87 minimum that the majority of cars require. 15% brings the octane up to 88/89.
We still have E0 87 available but it's about $0.40 a gallon more.