The American Petroleum Institute has filed a lawsuit to block the EPA's waiver allowing E15 in late model (post 2007) vehicles, on the grounds that the potential harmful effects from E15 have not been fully studied.
I agree with the API, at the heart of it. If E15 is sold alongside E10, some customers may try to use it in older vehicles, and they could have problems.
However, on the practical side, I don't see E15 going anywhere in this piecemeal permitting approach. For E15 to have any impact, it will have to be mandated, not just permitted. And I doubt it will be mandated until it has been proven safe for older vehicles. Considering that the average age of cars on the road in the U.S. is around 10 years or so, to safely cover most used cars EPA needs to test back well before 2001 model year. I don't have the data (R.L. Polk, where are you?) but I suspect you would have to go back to like 1995 to cover 95% of the vehicles on the road.
On the commercial side, gas station owners are not about to spend $ 20,000 per pump to upgrade to E15 certified pumps. According to this NY Times piece, unless there is a mandate, gas stations are not going to be switching over.
The third option for service station owners is simply not to sell E15, which Mr. Eichberger said seemed likely. ”It is an authorization without a mandate,” he said. “There is no retailer out there who has to sell this product.”
E15 will remain mostly a symbolic gesture for the near future. And if your favorite station does put up signs warning you that they are selling E15, make sure you don't put it in your older car, boat, 4 wheeler, or lawnmower.