Maybe it was the trucker in New Mexico who poured beer over his corn flakes, or the Elvis clone in South Carolina who ate fried clams at 8 a.m. and declared: "Eating breakfast is dumb - like a dog wearing feathers," or the Hollywood screenwriter who advised, "The measure of man's retreat from the centers of civilization is gained by adding the age of the rye bread to the amount of butter on a corned beef sandwich." Somehow Jane and Michael Stern became addicted to the Great American greasy spoons that lie scattered about the land in the shadows of the Golden Arches.

"Their great strength," says Jane Stern, "is that they offer all the advantages of home cooking without the obnoxiousness of your relatives."

It was, in fact, Jane Stern's trailing of truck drivers, for a book called "TRUCKER: A Portrait of the Last American Cowboy," that started her, her husband and their now-traded-in VW Rabbit on a five-year quest for road food, which became "Roadfood," a kind of Duncan Hines Guide for the low budgeted.

"The first thing you learn," says Mrs. Stern, "is how wrong the old ad-age of truckers knowing where to eat is. Follow the trucker and you'll find the next microwave oven."

"At first we would pull into a town and ask where we could get a good meal," says Michael Stern who, like his wife, is 31. "Well, to most people, good means the most expensive, and you're in some faraway place and they tell you to eat at the Holiday Inn. So we learned. You ask people, 'Where would you eat,' and they say, 'Well, I'd eatat Joe's, but you - you would probably like . . . the Ramada Inn.' And you ask the right people, especially cops and postmen."

"There are certain things you get to look for," says Mrs. Stern. "No out-of-town license plates. Where the sheriffs car is, Rodeo posters in the window."

Just the sort of place they were eating in the other day: The White Palace in Purcellville, Va., which has been dishing out home-cooked food since the early '20s. Mrs. Stern was impressed with the creamy thick shakes made with real ice cream. The town sheriff wandered in during the meal, there were some local concert posters in the window and narry an out-of-state tag could be spotted in the streets.

After all their work, the Sterns wound up with not only a book rating over 400 roadfood spots, they also got their fill of America. At their very favorite spot, Mrs. Bromley's Dining Room in Clarendon, Tex. (which is actually the dining room in Mrs. Bromley's house), the roaming gourmands got so stuffed that Mrs. Bromley offered them a nap upstairs between portions of the meal.

"There are more great roadfood places in Texas than anywhere else," says Michael Stern, who also claims that Kansas "is the wierdest place in the country, probably because it's so far from any coast.

"It was around Kansas City," says Micahel Stern, "that we had this very strange experience. They have a thing called Brownies in the midwest - cut-off ends of the barbecue that are incredibly tasty. We pulled into a place that had a big sign up for Brownies, and we went in, and asked for a plate of Brownies, and the waitress said she didn't understand, and then another waitress came out, and we asked for a plate of Brownies, and she said she didn't understand. Finally we found out - that the guy who owned the place was named Brownie."

"I think," says Mrs. Stern. "that they thought we were a Manson group."

She is an art historican, with a degree from Yale, where she met Mr. Stern, who was studying the same thing. They live in Connecticut now, and his commutes to Columbia a few days a week to teach film. If Michael stern ever finishes writing his dissertation on the films of Douglas Sirk, he may get that Ph.D. from N.Y.U.

But, as Jane Stern points out, films are films and a french fry is a french fry is a french fry.

"Eating is a joy of life," she says "but when I think of movies I'm reminded of Rock Hudson in Magnificent Obsession.' What did he say? 'To me, art's just a guy's name.'"