E85 won't work in these cars. Ethanol needs a specially designed engine, like those in flex fuel vehicles, to run properly. While all gas can contain up to 10% of it, it's limited to that because most petrol engines can't burn more than a 10% concentration of ethanol properly. Also, as you can see just by the numbering system, E85 has a lower octane rating than what is allowed by manufacturer's specs. That will cause pre-detonation. Putting a higher amount of ethanol in a petrol engine most likely will cause catastrophic failure or at least gunk up your fuel system/engine pretty bad. I don't specifics right now though.

There's a good amount of gas treatments available at stores like Autozone, etc. If they don't have any, or even if a gas station didn't carry any inside, I would be really surprised. If you want to fill the empty space in your tank, get a hold of some gas treatment if you can, then go to another station and fill up. Make sure to check on the pump and see when was the last time they were certified by the DoA. They have to be certified once a year for the same month, so don't be alarmed if it says "Oct 2009". It's certified until Oct this year when they'll retest it.

EDIT: Here's an example of what to look for when looking for gas treatment- http://shop.advanceautoparts.com/web...ci_sku=7080522

I would expect Walmart to have that. Every Walmart I've been to did. Just remember to follow the instructions on the back of the bottle.