What's the difference between a collector and a hoarder? I often wonder as I tour garages. A thread certainly binds the great ones: they're packed with neat stuff. As a whole, car people are wonderful gatherers. It's largely from necessity; owning obsolete things makes us rather opportunistic.

But the line separating collectors and hoarders isn't so clear, at least according to two behavioral scientists who answered-or at least tried to answer-that question on the radio one evening. They'd just recently published a book on the subject, and given the popularity drummed up by reality hoarding shows of late, they found a forum on one of my favored interview programs.

What made that question stand out was the day that preceded that particular evening. Actually that question more than stood out; it gave me the heebie-jeebies. It would have you too were you in my position. I thought someone was messing with me. I looked as calm as possible. Then I glanced furtively for a camera.

No more than 30 minutes prior I'd left Alan Darr's house. Alan collects petrolania, the hardware and marketing material generated by the petroleum industry: globes, pumps, signs, advertisements, and so on. As far as petrolania collections go, his is one of the more sought-after.

But what makes Alan's collection so coveted is not its size as much as its focus: for around 40 years he specifically collected items created by and for the Gilmore Oil Company.

Gilmore, if you didn't know, has a special place in the petrolania world. For 45 years it did more than sell gas, oil, and service; it basically facilitated America's love affair with the automobile. And in doing so, Gilmore produced a seemingly unnatural amount of stuff: packaging, advertising, flyers, cards, pens, matchbooks, license plate toppers, and ashtrays. And that's not to say anything of the pumps, globes, signs, and other things used in the distribution of petroleum products.

And if Gilmore made it, Alan Darr might have one. That's what made the program so compelling: Alan has packed a good part of his house with Gilmore-related items. Every square inch of his two-car garage's perimeter is chockablock with signs, banners, plaques, displays, and so on. As the collection grew, it spilled over to fill all but 6 or so square feet of one of his home's bedrooms. How would these experts judge Alan? I listened, and wondered.

It all started with the Model T

They say that Henry Ford's Model T put the world on wheels. Henry's T certainly put Alan Darr on his path. "I had a '27 roadster pickup and I thought, 'Gee, it would be kind of neat to get an old gas pump,'" he says. "I worked for the fire department. Everyone had to have a little sideline job because you couldn't live on what they paid you at the fire department. I was kind of into old cars ... so I'd just buy parts and advertise them in Hemmings. I'd see a '40 Ford coupe behind some guy's house so I'd ask about buying parts off it. I'd take the money I made from that and go onto something else.

"Along the way I'd find signs and artifacts, and most of that stuff I'd end up keeping. So eventually I was buying and selling parts so I could buy more signs and pumps and so forth. That stuff was starting to get hard to find. People were grabbing it whenever it showed up. I was taking just about whatever I could get my hands on."