The office is easy to miss. The drab, one-story building in North Hollywood, Calif., has no business sign, just street numbers.

A brick wall topped with barbed wire surrounds the premises. Windows are barred. Beyond the black iron gate, a brown Mercedes is parked. Its license plate reads "Capn."

Inside, past a maze of doors, behind an untidy desk in a small office cluttered with books, papers, a movie projector and videtape equipment, sits the "Cap'n" himself -- an oil industry legend who has spent his last 20 years charting the ebb and flow of the gasoline business.

White-haired, with goatee and mustache, wearing a dark blue pin-stripe suit and red suspenders stretched over his ample middle, Daniel Lundberg is on the telephone.

"I live a life of undeviating rectitude," he bellows into the receiver at a potential client. "Look what the dear Lord has done to me, or maybe it's Satan. They're in cahoots over me."

Dan Lundberg, publisher of the Lundberg Letter, a weekly compilation of charts, graphs, pronouncements and analyses about oil marketing, is an enormous bear of a man -- loud, energetic but gentle, and at times pompous and crude. Punctuating his points with sharp jabs to the arms of his listeners, his blustery presence fills the office as surely as his name has been filling the news.

Frank N. Ikard, former president of the American Petroleum Institute, now a senior partner in a Washington law firm, calls Lundberg's letter "as reliable a service as there is."

"Ever since I've been in the industry, he's been around," Ikard says, "but the media have suddenly discovered him. He wasn't doing anything that the average man would have been interested in prior to 1973.

But then the oil embargo hit, the "energy crisis" became a household lament, nd Americans began to wonder just how much gasoline was going to be available for the family car. Lundberg was thrust into the media spotlight last March when he predicted -- with unnerving accuracy -- an 8.9 percent shortfall in gas supplies and long lines at the pumps. Since then, he has become the main pipeline of information about gasoline supply and prices through his private marketing reports and through his newsletter with about 1,000 subscribers in industry, government and academics. His combined operations gross over a million dollars a year.

"As the oil story became an important story, one generally found there was a limited number of sources about oil," says Irving R. Levine, economics correspondent for NBC News. "Most of the sources had some built-in bias . . . but Lundberg is a rare species."

"He's his own man, and there are damned few of them in the oil business," agrees Associated Press business writer Stephen Fox.

Even the Department of Justice relies on Lunberg. In a recent California case in which a gas-station owner was convicted in federal court for overcharging, Lundberg's material was entered in evidence by the DOJ.

His life has not been the same since last year's gas lines. "That's when the interest really began," he says. "People started to say, 'Call Lundberg. That-------knows what's happening.'

"Everybody wants to know why, why, why. But answering those questions makes it difficult for me -- I've got to run a business."

He was a long time getting into the business. Born 67 years ago in New Britain, Conn., Lundberg has been a novelist, CBS correspondent, diplomat, TV talk-show host, news anchorman and public-relations agent. Along the way, he accumulated two marriages, five children and a life-time of travel.

The son of an itinerant violinist who also directed the Swedish-American glee club, Lundberg never completed college, although he attended 11 of them.

"What I was, was a college hobo," he says. "I was a college roustabout. We had an old Hudson Super Six when I was 18 years old. We tore the top off, put a stand on it and put a railing around it. We had drums, a tuba, a tenor, an alto sax, and with me on trumpet, we just barnstormed. We'd go into a community and rent a hall."

Lundberg and his group would enroll in one school after another to become the college band.

Selling yearbook advertising provided some income; so did writing -- as a freelance correspondent for Esquire magazine and as a novelist. In 1941, at the age of 28, he published a book called "River Rat" about young people living on the Charles River in Massachusetts. The novel, he says, "is so much like J. D. Salinger's 'Catcher in the Rye' that if you compared the two, you'd have spots in front of your eyes."

The novel brought favorable reviews, though its success did little for Lundberg's career as a writer. "I'd still be a novelist until this day, but the Japs shot me down," says Lundberg. As an asthmatic, he had no military career, but the advent of the war meant book sales were down, and he had to look elsewhere for a living.

He lived in Mexico during the war years, at first producing anti-fascist radio plays. Later, he moved into the news media.

While running a CBS-operated short-wave radio network and serving as CBS correspondent from Mexico, Lundberg also went to work for the U.S. State Department after Franklin D. Roosevelt appointed Nelson Rockefeller undersecretary of state.

With the end of the war and after a brief stint covering the founding meeting of the United Nations, Lundberg found there was a glut of CBS foreign correspondents returning from abroad. He says that Nelson Rockefeller, at that time, "gave me some avuncular advice.

"He said, 'You'd make a pretty good PR man.' I said, 'Where would I get any accounts?' He said, 'You know -- it's the oil industry.'"

Lunbderg waited a while before he took the future vice president's advice, and first became a news director at a Pasadena, Calif., radio station. One day the owner of a small chain of self-service gasoline stations heard Lundberg, in a commentary, flailing away at the powerful opposition to the rapidly expanding self-service gasoline business.

"I was so dumb, I didn't know a safety nozzle from a spark plug," Lundberg said later. "But I did know this: The self-serve needed to be organized."

One thing led to another, and a movement was born. With Lundberg leading the charge, the Serve Yourself Gasoline Stations Association, Inc. took its battle cry around the country, winning victories against the conventional dealers and jobbers who saw high-volume, cheap gas as a threat.

"We won all the battles, and I was running out of issues," says Lundberg. He stayed in his public relations business with the Calfiornia Petroleum Distributors Association and the Automatic Laundry Association as clients. At the same time, he held down a job as anchorman at KNXT-TV News (the Los Angeles CBS affiliate) where his announcer was an up-and-coming young man, Johnny Carson. Later at another TV station, he hosted "The Dan Lundberg Show," an interview program.

By the mid-1950s, Lundberg, perceiving a need, terminated his public relations business, severed his connections with the trade groups and instituted Lundberg Survey, Inc. At the time, he says, gasoline prices were turbulent. "There was pandemonium. Nobody knew what the hell was going on."

His survey of gas prices began in 1956, selling over the counter. And "it grew like Topsy."

Apart from one interlude it's been growing steadily ever since. In 1966, Lundberg took time off and sailed his wife and three youngest children across the Atlantic, braving a hurricane in a 50-foot ketch. (He still sails.)

In Rome, Lundberg produced a record album, "Nero Fidicen" ("Nero Fiddles") -- a musical comedy in Latin with an anti-nuclear war message in which his daughter Trilby played the piano. The music was written by Bill Conti, who later wrote the score for "Rocky."

But after all those colorful years, when Lundberg says, "I'm going to tell you something that's going to knock you off your feet," he is talking about his business. And he launches into a discussion of his invention called COMPROF, for "comprehensive profile," a shorthand using numbers and letters which allows him to encode information about gas stations into a form computers can deal with.

Lundberg has assembled a nationwide army of more than 250 "stringer-correspondents" who fortnightly survey 16,700 gas stations and report back in computer code -- not only on prices, but on such items as whether the stations are split islands, serve diesel fuel, rent trailers, do brake work or wash cars.

Then, using tax information from all 50 states as well as statistics furnished from any number of sources -- oil companies, the Department of energy, the American Petroleum Institute -- Lundberg, his staff, his IBM Model 370 computer and his printing press spew out piles of statistics broken down by cities, states or other geographical regions, and customized for his clients (he won't say how many). He puts his findings in the newsletter.

He has occasionally caused headaches for oil industry public relations people. Last October, the Lundberg Letter raised the specter of another round of gas lines for that month. The story was immediately picked up by reporters around the country who began bombarding oil company executives for reactions. "He's blowing smoke," responded a Shell Oil man in Houston at the time. The experience left a bad taste in many mouths, since no crisis materialized.

Lundberg recalls the incident angrily. He called the Shell spokesman after his quote appeared in print, Lundberg says, and told him, "You subscribe to all these surveys -- you cancel them if they're no good." Lundberg blames the media for exaggerating his prediction, offering the text of his October forecast which held out "the possibility of long waiting lines at service stations in some markets," and added "there are grounds for hope they can be averted."

Lundberg is his own most enthusiastic booster. He points proudly to a photo: "That's me with A. C. Nielsen. Together, we measure the world." But users of his services say that Lundberg's information often provides the basis for marketing and price decisions. Lately, however, since stringent Department of Energy regulations restrict profit margins and thus pricing flexibility, the usefulness of his surveys has somewhat diminished.

"When they nationalize the industry, that's when they'll kill me," he says. In the meantime, however, business is good.

About 16 billion gallons of gasoline are sold domestically each year, and Lundberg, more than any one person in the country, can tell you where it goes and for how much.

He picks up one of his charts on gasoline consumption: "Look at this incredible, gas-guzzling nation."