With each day that oil fouls the Gulf of Mexico, more drivers are weighing a choice at intersections across the United States: if BP is on the left and some other station is on the right, is filling up at BP an endorsement of the company’s conduct?

Advocacy organizations like Public Citizen urge consumers to stay away from BP stations. About 550,000 Facebook users have clicked the “Like” button on the Boycott BP page. And angry people have picketed at BP stations.

This doesn’t send a particularly powerful message to BP, though. After all, BP owns only a handful of the 11,000 stations that bear its brand and is trying to sell the few still on its books. So those who wish to inflict the maximum amount of pain on the company are instead putting much of the hurt on the family businesses that actually own the stations.

Just how little does BP gain from its gas stations, besides whatever ancillary marketing benefit it gains from the signs? The gas in its pumps may not be extracted, refined or stored by the company and may just get a spritz of BP additives right before it ends up at the service station. All of this puts a mere handful of coins in the company’s pocket per fill-up.