A year-long campaign by area government and business leaders to get Mobil Corp. to move from New York City to Washington apparently has been successful.

What remains to be done before Mobil, the seventh largest industrial coporation, makes an official announcement, is to get final agreement on rezoning and traffic plans for the projected headquarters.

The 130-acre site on which Mobil has an option is located near Falls Church in Fairfax County. Up to 4,000 Mobil employees are expected to work there eventually.

Officially, Mobil spokesmen say that "no final decision has been made." But interviews with government officials in Northern Virginia, Richmond and New York last week made it clear that the move is all but certain.

Fairfax County planning officials expressed the hope last week that hearings on rezoning will be completed in the next two months so that final action by the county's Board of Supervisors can clear the way for Mobil by mid-June.

If current timetables are met, construction could start before the end of 1977 and the first Mobil employees would begin moving into their new offices by the end of 1979.

Gradually, Mobil would relocate most of its headquarters operation here while retaining some executive offices in New York - reportedly including that of company chairman Rawleigh Warner Jr., who has a home in Connecticut and wants to stay in New York.

John Herrity, chairman of the Fairfax supervisors, said "nothing" could stop Mobil's move here "if we can put together" a combined transportation, rezoning and environmental impact package for consideration at hearings in the near future.

A key element in the economic development process affecting the proposed Mobil site is a task force of county planners, land owners and citizens. For two years, the task force has been studying recommendations for future use of the land involved - part of a 185-acre plot bounded by the Capital Beltway, Route 50 and Gallows Road, owned by the estate of Earl N. Chiles.

According to Virginia officials, the task force is about to make its formal recommendations to the Board of Supervisors, after which public hearings would be scheduled.

Williams Hansbarger, attorney for the Chiles estate, said Mobil plans to outline its final plans to the task force on April 13. State of Virginia officials will detail proposals for highway access to the Mobil site at the same meeting.

Herrity confirmed last week that he met with Gov. Mills E. Godwin in Richmond on March 25 to seek state aid in attracting Mobil. Specifically, Herrity said, "We are developing a proposal to be submitted to the citizens group, which would have the effect of resolving transportation problems at Route 50 and Gallows Road."

Involved is a $7.5 million package of state highway improvements over "a period of time," to which Mobil would contribute by buying about 15 acres of land needed for the road development, Herrity stated. There would be no cost to Fairfax County.

Two alternative are being studied for the Route 50-Gallows intersection, where traffic volume would be boosted graduatlly as Mobil phases in additional offices here. One plan would channel Gallows Road over Route 50 with a cloverleaf, and the second plan involves a large ramp exit. The expense would be about the same for each, sources said.

Godwin, who reportedly advised state and Fairfax County officials that he wants to do whatever is necessary to attract Mobil, told The Washington Post: "This is a very desirable type of business operation for Virginia, and the state government is cooperating in every possible way with the authorities in Fairfax County to encourage Mobil to locate there."

Mobil would be the largest corporation based in Virginia as well as the largest in Metropolitan Washington if a decision is made to move to Falls Church.

With 1976 sales of $28 billion (up from $22 billion the previous year), Mobil Corp.'s annual revenues far surpass Reynolds Metals Co. of Richmond, currently the state's largest industrial firm with sales of $2.1 billion last year. Worldwide, Mobil has 199,500 employees.

Subsidiaries of Mobil include Mobil Oil, the nation's third largest petroleum company; Montgomery Ward & Co., one of the 10 largest U.S. retailers, with 430 departments stores; and Container Corp. of America, the largest U.S. manufacturer of paperboard packaging.

Although Mobil has diversified beyond its oil base, petroleum profits accounted for $772 million of the $943 million Mobil earned last year.

Mobil announced plans last year to move an 800-employee domestic marketing and refining division from New York City to the Northern Virginia location. After additional studies of the Washington area and its own employee attitudes, Mobil started to study the possibility of moving nearly all its 2,700-person corporate headquarters from Manhattan.

Mobil chairman Warner was on vacation last week and unavailable to comment on the reports that a firm decision has been made to relocate here provided zoning is approved.

Informed sources in New York said, however, that Mobil plans to move almost of its headquarters employees here - not just some of its central staff.

According to these sources, Warner has indicated to New York City and New York State officials in recent meetings that his company is preparing within two or three years a larger move of central office personnel to Fairfax County.

New York City has formed a group of business and labor leaders - including Chase Manhattan Bank chairman David Rockefeller and Pfizer, Inc., chairman Edmund Pratt Jr. - who are putting pressure on businesses that are thinking of moving out of the city.

Reportedly, in conversations with city officials, Warner indicated that he would keep his personal office in New York and that there would be a small executive office as well. Mobil personnel said Warner does not want to or would not move down to Washington.

In addition, there also is resistance from many of the company's employees who now live and work in New York - particularly those involved with extensive public relations, media and advertising operations and who therefore have to deal daily with people in New York and for whom the "action" is almost completely centered there.

Publicly, Mobil has said it will decide by Sept. 1 whether it will move more than the 800 employees south. Sources said the company management believes the promise of more jobs for Fairfax County inherent in an almost total move of its headquarters from New York would facilitate favorable zoning rulings.

Mobil's international headquarters is in its own building on 42d Street between Lexington and Third avenues in mid-Manhattan.

Although metropolitan Washington business leaders have begun to develop an aggressive campaign in recent years to attract new business here, the decision by Mobil is not a direct result of such promotions.

One businessman familiear with Mobil's operations said the company has found that it simply could no longer attract young executives to its New York offices, even for promotions from jobs in other cities. Mobil officials reacted by searching for other sites and picked Washington because much of the energy industry's future is tried to federal government decisions. The American Petroleum Institute, trade group for the oil industry, moved here from New York in late 1970.

A survey of Mobil managerial and professional workers around the country, who were asked about moving to New York with a promotion, found that 80 per cent were willing to work "any place but New York."

Business and civic leaders here expect Washington to blossom over the remaining years of the 20th Century as a site for corporation headquarters or major offices, mostly at the expense of New York and mostly reflecting a desire to be near the center of economic decision-making in the federal government.

Washington already has replaced New York as the capital of trade associations, creating a local industry that employs more than 40,000 persons. Time, Inc., moved its book division here from New York last year, and the aerospace and construction materials firm of Martin Marietta Corp. recently moved into its new Bethesda headquarters complex, after leaving New York.

Informed business community sources said one other petroleum company, said one other petroleum company, said to be smaller than Mobil, is considering relocating here, and a spokesman for the Metropolitan Washington Board of Trade said serious negotiations are in progress with four national companies that are studying Washington.

Three of the four companies are considering the relocation to Washington of some facet of their business - decisions that ultimately could lead to the same type of action reportedly made by Mobil.