http://www.sierraclub.org/sierra/pickyourpoison/
Realistically, most of us won't be able to completely abandon fossil fuels tomorrow -- American drivers still consume nearly 400 million gallons of gasoline per day. But where we choose to buy that gas can send a message provided we know which oil companies are doing the least harm to the planet. Sierra magazine updated its rundown of the eight largest U.S. oil companies, and the results are posted as an on-line exclusive now.
Bottom line: Which corner station you pull up to can make a difference. No prizes for guessing where ExxonMobil shows up in the rankings, either.
I think Citgo belongs in the top group, but hey, it is their guide.