Standing at a gas pump yesterday, I thought about what oil expert Daniel Yergin told me during a recent interview.

"When you're filling up your car, you aren't just filling up your car," he said. "You're plugging into a very large part of the world economy. Behind every gallon we pump, there is a huge logistical system that moves 77 million barrels of oil a day."

I could almost hear the earth gurgling beneath me. Obviously clueless about how this vast fuel delivery system really works, I was still very much aware that no matter where I drive there is usually a gas station within a few miles, if not blocks.

And that's just the way I like it.

Lately, though, with America at war and oil once again in the backdrop, having a "gas 'n' go" mentality no longer feels quite right.

This summer, a group of environmental activists on bicycles blocked my access to a gas station on Capitol Hill. They were carrying banners that read "Bikes Over Big Oil," and they pledged to stop any attempts to drill for oil in Alaska's Arctic National Wildlife Refuge.

I had never come so close to deliberately running over somebody before. But I have since cooled down and even tried to understand why the bikers would risk their lives that way.

One of their environmental publications, the Sept. 20 issue of Greenwire, was almost as provocative as the protesters.

"At the core of international outlaw Osama bin Laden's militant opposition to U.S. policy and presence in the Middle East is a matchless commodity that underpins the American economy and bankrolls Persian Gulf governments," wrote Colin Sullivan, a staff writer. "Indeed, if not for oil and the American thirst for it, not only would policy dictate a far less imposing U.S. military presence in the Middle East, but bin Laden's campaign against the United States and the oil producing states it protects would likely be far less severe, according to foreign policy experts."

And there was this editorial in a recent issue of the Earth Island Journal: "Our foreign policy is captive to oil. If you were to draw a flow chart tracing every terrorist attack against the United States back through every foreign alliance, military mutual aid pact, joint military exercise, bloody political coup, intrigue and tacit alliance, the lines would generally flow back to one common factor. Oil."

And yet, attempts to reduce dependence on foreign oil could play into the hands of those who support drilling in the Alaskan wildlife refuge.

The alternative, says the Earth Island Journal, is to discontinue an American foreign policy that props ups dictatorships and repressive regimes and to "transform our economy into one that operates on clean, renewable energy."

While intrigued by such viewpoints, I couldn't wholeheartedly endorse a group that rides bicycles in front of cars headed for a gas pump. Especially my car.

Yergin, on the other hand, is no radical. He taught at the Kennedy School at Harvard University and was author of "The Prize: The Epic Quest for Oil, Money and Power."

He's not even anti-automobile.

"My favorite statistic in the whole book has nothing to do with the price of oil," he said. "It has to do with the fact that 40 percent of American marriages are proposed in automobiles, which I take as one of the great signposts of the hydrocarbon society that oil has made possible."

But all is not well.

Despite recent progress in developing more fuel-efficient cars, Americans don't seem especially impressed. "Probably the biggest thing that has happened is the American passion with SUVs, which are not as fuel efficient as automobiles," he said. "Half of all cars sold are SUVs, which is, in a sense, a sign that people are not very concerned about the stability of the oil supply."

As the ground war was reportedly getting underway in Afghanistan, I couldn't help but wonder whether my penchant for squeezing the trigger on that gas nozzle was in any way connected to American troops now having to squeeze the triggers on guns abroad.

Yergin had only encouraged more questioning.

"Maybe you could say that in times like these, it's not enough to just gas and go," he said. "It's also a time to gas and think."

E-mail: milloyc@washpost.com