Organic food is successful because a significant number of people believe it is healthier to eat than non-organic foods. The environmental impact is mostly not the reason. (Whether it is true that organic foods are healthier may be debatable, though for some foods the evidence is pretty good that it is.)

It won't work to use that angle for gas. Pure environmental plays are harder to find. There are people who pay more for renewable generated electricity, so that's a good parallel. I don't know what percentage, however, or if it'd be enough to support a chain of expensive gas stations.