So what interest do the oil producers have in this other than the fact that they want you to buy gasoline instead of ethanol? How else are they being hurt by it?
Any time the government mandates changes in the formulation of fuel that is not scientifically supported it means that somebody is going to get rich (the corn producing farmers and their congresscritters like the new SD-RINO Kristi Noeme) and somebody is going to get screwed (the American consumers of that fuel).
The oil companies don’t have much to do with it. They will produce the fuel and the governement will mandate its adulteration into something that is harmful. Do you remember MTBE?
Additional varieties drive up inventory costs. Plus if this ethanol mix is even more hydrophylic, it may damage their own equipment.
Refiners, pipelines, wholesalers, retailers, and drivers hate, or at least should hate, ethanol because it is hydrophilic. Water readily separates from petroleum hydrocarbons (i.e., oil and water don't mix), but it mixes readily with alcohol. Thus, you can easily get water mixed into motor gasoline since the ethanol mixes with both water and gasoline.
The oil refining and marketing industry is also concerned about performance issues of using ethanol in their customers' automobiles. The EPA and the rest of the USG doesn't care if their mandate destroys your car's engine, but businessmen actually want their products to work well for their customers. It's bad for business. For some reason, government screws up over and over again, but it still gets paid because it can coerce taxpayers. Businessmen rely on voluntary customers for their livelihoods.
How would your company be hurt by being forced to sell products with 15% composition made by a competitor?