Hi
bsantelli - I just joined this forum recently, and discussed this topic on another forum, so I'm late to this thread, but here's what I think...
1)
Reason to Avoid Ethanol: The risk of fuel system and engine damage, and if not lesser performance, think of inadequate operation, such as being hard to start, sputtering, computer de-tuning, even "downstream" issues such as shifting smoothness, etc, etc. Warranties depend on your model's ratings. For the 2012 V6 Coupe, 87 E10 is the minimum standard, but that by no means implies that minimum is ideal. Far from it, if that 87 E10 is some low-end brand.
2)
Impact/Benefits, even if Occasionally Used: If you use a "
Top Tier" brand, then the additives and detergents in their gas will clean the system and help reduce or eliminate the threats from corn gunk that builds up from lower-end ethanol blends. If you use a no-name crap brand, it might not matter what grade or blend you use, because it's all crap

If you use a Top Tier E10, you might not notice much performance/mileage difference with the ethanol-free version of the same, but the benefits are still there, unseen.
3)
Station Percentages: It can vary as others said, but by late 2012 I think it was becoming pretty standardized at 10% corn alchohol. E15 is on the way, perhaps, and some cars run (barely) on E85. This is partly why the issue "snuck up" on a lot of us, even those of us who consider ourselves concientious buyers of premium gasolines for cars we care about, as most stations changed over from ethanol-free and/or light blends to E10 without warning, aside from the small stickers on their pumps. As time goes on, a not-small number of stations listed on
Pure-Gas.org are already, or are converting to E10-only, and so "pure" Top Tier gas is becoming harder to find. Where I live, near lakes and the ocean, it's more common to find ethanol-free as a "regular" 87 grade no-name crap gas for the few who require it. So, in that case (say on a trip and stuck in the wilds), is it better to run a crappy 87 ethanol-free from one station on that interstate exit, or pop across the highway for a top-of-the-line premium E10??
Anyway, hope all that helps (even if it's more than a year later)
