E5 or E10 can be tolerated by pretty much any vehicle built since the late 1990s, and many from before that. I don't have a problem with E10, even though I do get somewhat worse gas mileage - at that level the difference isn't really noticeable. E15's another story - many modern and most older cars WOULD have a problem with it over the long term. And E85 of course requires special fuel systems.

I'm also happy to hear that the corn consumption issue is being dealt with because it is a real problem. As with any oxygenate, though, ethanol reduces the energy content per gallon and modern cars compensate by burning more fuel. It's also a bit of a pain to deal with in fuel distribution because it can't be blended at the refinery - must be done at the distributor to avoid separation in transit.

Interesting tidbit: some years ago, California air regulators were looking at proposals to bring in bargeloads of ethanol derived from sugar cane. It would have been less expensive than corn-derived ethanol including shipping, and actually better from a total CO2 emissions standpoint (sugar cane - ethanol conversion more efficient overall) even with the shipping. Problem is, federal ENERGY (not air quality) law prohibits use of anything but corn-derived ethanol as a gasoline oxygenate - where did that come from?

I have no fundamental problem with biodiesel (diluted with ethanol or otherwise) either. It's a great way to go, and might even relieve some pressure on diesel prices at the pump if done in quantity - most refineries in the US are optimized for gasoline production so diesel is a byproduct (unlike in much of the rest of the world). Main issue would be: what's the source? If it's a food crop we're back into the same little scuffle as with corn. And does that proto-Tier 5 engine require biodiesel or can it run on something else (and does it require SCR aftertreatment which was part of the original complaint here)?