It seems there is a lot more to switching from Ethanol 90/10 to 85/15 blended gas than just making it and pumping it through the same lines, thus initially mixing it up for a few days.Having spoke with Fire Personnel in on the loop. It involves everything from the Factory, its lines to the interstate Pipelines to the Metro area tanks and the 1203 Semi-Tankers hauling gas. All must all be must be made ready for the switch.
Note: 15% based fuel is more likely to evaporate and be ignited by static electric discharges than 90/10, especially in warmer months.
The Gas Tank Farm (storage facility) in Doraville, GA area recently alerted Metro-Atlanta FD's they were starting the initial prep work for the switchover process and would be "temporarily" halting the incoming pipeline flow to do the work. Because the prep work itself would cause some additional potential fire and safety issues.
Gas prices are already increasing in many areas.
NOTE: In general, ethanol has about 33 percent less energy than gasoline. So, the more ethanol in the fuel, the worse the fuel economy you are going to get (Less Miles per Gallon).
BTW: Ethanol evaporation is a major source of air pollution in the USA. And it takes more energy to produce Ethanol for Gas than the Energy it saves using it.