Many remaining Americans reluctantly left Libya today, 24 hours ahead of President Reagan's deadline. At the same time, the U.S. 6th Fleet wound up week-long exercises near the disputed Gulf of Sidra.

Perhaps 100 U.S. oil workers -- ranging from field hands to executives -- and a few spouses boarded a variety of Europe-bound flights.

A number of them expressed disappointment at leaving and apprehension over their chances of finding new jobs in a shrinking world oil market.

"I'm hauling bottom out of here and going to Dallas," said a 60-year-old driller, "where I guess I get to go on the dole."

He and a colleague from Oklahoma, on a flight bound for nearby Malta, declined to give their names.

Other oil workers suggested that some of those requesting anonymity in talking to reporters were doing so to avoid alerting U.S. authorities if they did return here.

[In Washington, administration spokesmen said they have no evidence that U.S. oil companies that have been operating in Libya had shifted their assets to foreign subsidiaries or producers. But other officials acknowledged that the administration is negotiating with the four U.S. companies on finding orderly ways to dispose of their Libyan holdings under Reagan's Jan. 7 executive order barring U.S. citizens from any trade with or travel to Libya.]

The Americans' departure, if definitive, was viewed by western diplomats as more likely to harm Col. Muammar Qaddafi's government than the threat -- or even use -- of force. For if Washington's confrontation with Libya this month has allowed Qaddafi to play David to America's Goliath in domestic, Arab and some western eyes, specialists consider the prolonged absence of American oil technicians likely to hamper crude production in the short and medium term.

No incidents have been reported during the 6th Fleet exercises that began last Friday close to the Gulf of Sidra's 32.5th parallel. Qaddafi claims sovereignty south of that point -- which he dubbed the "line of death" -- in contrast to the view of many other countries that the gulf lies in international waters up to 12 miles from shore.

The maneuvers lent further force to the president's executive order requiring all Americans to leave Libya by the end of January in reprisal for Qaddafi's alleged role in abetting Palestinian terrorist attacks Dec. 27 at airports in Rome and Vienna.

After midnight Friday, any American remaining here would be breaking the law and could be disavowed by the administration if taken hostage in the event that military force is used against Libya.

But the Americans departing today -- who did so because European airlines do not fly here on Fridays -- left reluctantly and with nothing but good to say of the Libyans and their treatment here.

Just how many Americans remain in Libya is almost impossible to calculate, since most of them worked in the oil business and rotated in and out of the country. Since the president's executive order, the State Department has estimated that up to 1,500 U.S. citizens were living in Libya.

For the minority of Americans here with families, complicated formalities and the paucity of moving firms made western diplomats doubt that all could meet the president's deadline.

Moreover, departing oil workers confirmed reports that some oil and service companies were promising their American employes that their jobs would remain open for a month -- sometimes with pay -- and in some cases for as long as a year in hopes that the administration would relent.

Those offers reflected Libya's continuing dependence on American know-how for its almost totally U.S.-designed and -equipped oil operations.

"If Qaddafi could have done without the Americans, he would have done so after Reagan ordered them out the first time in 1981," a western diplomat remarked.

Several departing American oil workers said they were concerned that their well-paid jobs here were being taken by Britons or Canadians, leaving them unemployed in a contracting U.S. and world oil market.

Many departing Americans said they fear that they might be forced to break the law and return if they fail to find other jobs.

Neil Blue, at 44 a nine-year veteran with an oil service company, flew in from a desert oil field this morning to catch his flight to Europe and feared facing unemployment at his home near Denver.

"I think 99 percent will be out by the deadline because that is the law," he said. "The risk is too big" for American businesses to defy the executive order, which many Americans here want challenged in the courts.

Although since 1981 Libya has allowed Americans to enter without stamping their passports, Blue showed a healthy respect for the punitive capability of the administration.

"They know the day I came in and the day I left," he said, "and they can check my airline tickets to prove it."

He said he had "stuck it out to the end because I needed the money and to train replacements."

The most bitter note was struck by one of about 100 American women who have elected to stay behind with their children and their Libyan husbands.

Shelley Ashureq, a 22-year-old mother of two from Portland, Ore., who works at the school run by Libya's national oil company, was especially angered by the form she had just filed with the U.S. Interests Section of the Belgian Embassy.

Referring to the waiver on humanitarian grounds required by the Foreign Assets Control Office in Washington to conduct "prohibited transactions," such as buying groceries, she said, "I never thought I would have to apply for a license to eat."

"What am I to do? Leave the kids, leave my husband and say goodbye and go away?" she asked. "My husband and children are subject to Libyan exit visa laws." She added that those formalities often take a long time here.

As for the likely effect of Reagan's confrontation with Libya, she replied, "He has just made people like it here more than ever. He's given people here bigger heads than they had before."

Many diplomats here have expressed the view that Qaddafi not only has benefited from domestic and foreign support during the confrontation, but will seek to perpetuate the tension to silence previously growing local criticism.