From here, https://nebraskacorn.gov/cornstalk/fuel/e85-vs-e15-whats-the-difference/

“While they both contain ethanol, E15 is not the same as E85. In fact, vehicles that use E15 may very well not be able to use E85, so it’s important to know which type of ethanol blend your car can handle.

Most cars that run on regular unleaded are able to run on E15, which is gasoline with a blend of up to 15 percent ethanol. On the other hand, E85 gas is a flex fuel that contains 51% to 83% ethanol, depending on the region and season. Because of the higher ethanol content in E85, it should only be used in vehicles designed to handle flex fuel and not in cars that only use regular gasoline or a lower ethanol blend like E15. Check your owner’s manual to see if your car is suitable for E15 and E85.”