A Marathon battle for Mobil?

Will Mobil Corporation, the nation's second-largest oil company, be able to buy Marathon Oil, the nation's 17th-largest, without an antitrust battle in Washington?

This question will be paramount if Mobil is to succeed in its second takeover bid within three months. In August, Mobil lost out in a three-way battle for Conoco Inc., the nation's ninth-largest oil company. Although Mobil said at that time it thought it could win Justice Department and Federal Trade Commission support for its cause, enough shareholders had doubts - raised in part by Conoco - that the shareholders tendered their Conoco shares to the Du Pont Company for

Mobil is sure to face these same antitrust arguments once again in its $5 billion bid for Marathon. Already, Sen. Howard M. Metzenbaum (D) of Ohio has issued a statement decrying the proposal. He is urging the Justice Department ''to act swiftly and decisively to block the merger.'' The Justice Department, which had reviewed the antitrust issues last summer when Mobil battled for Conoco, said the Mobil bid for Marathon would also be reviewed.

On Wall Street, analysts raised some doubts about the prospect. Joel Fischer , an oil analyst at Drexel Burnham Lambert Inc., told the Monitor he thought there could be some antitrust ''vulnerability in the refining and downstream (service station) operations.'' Mr. Fischer says it is possible that Mobil could find itself defending the takeover before Congress. An aide to Senator Metzenbaum, in an interview, told the Monitor the senator intended to ask Sen. Strom Thurmond (R) of South Carolina, chairman of the Judiciary Committee, to hold hearings on the proposed takeover. The senator's committee is holding hearings on the bid LTV Inc. is making for the Grumman Corporation.

For its part, Mobil, in a press release, said it believed the acquisition ''would not violate the antitrust laws.'' Mobil filed notice of its offer with the FTC and with the Justice Department's antitrust division. Under the Hart-Scott-Rodino Antitrust Improvements Act, the government has until 11:59 p.m. Nov. 14 to take action to block the merger. Should the agencies ask for more information, there would be a further waiting period for government action -- 10 days after the date Mobil complied with the request for information.

Antitrust problems won't be Mobil's only obstacle in the takeover.

Wall Street analysts believe Marathon may search for a ''white knight'' -- a corporation it would consider more desirable as a takeover partner -- to try to outbid Mobil. As Mr. Fischer asks, however, ''Who could outbid Mobil?'' Names mentioned prominently in this connection include Texaco, which considered bidding for Conoco; Gulf Oil, which has lined up a multibillion-dollar line of credit; Standard Oil of Indiana; the Atlantic Richfield Corporation; and the Allied Corporation. Analysts believe an OPEC country, such as Kuwait, or a foreign company might also be interested.

Mobil is likely to face strenuous actions by Marathon, too. Although the Findlay, Ohio, company said it had no comment about the bid, Marathon is known to have lined up $6.3 billion in credit that it could use to short-circuit the merger attempt.

The Ohio company is also likely to try to use state antitrust laws to stop the bid. As a defensive step, it said it was commencing legal action in the US District Courts in Louisiana, Ohio, Nebraska, South Carolina, and Utah to restrain those states' takeover statutes as unconstitutional.

Mobil's chairman, Rawleigh Warner Jr., said Mobil was buying Marathon ''in accordance with the longstanding Mobil policy of acquiring and developing oil and gas assets.'' It noted that recently Marathon had bought the US oil and gas subsidiary of Husky Oil Ltd. of Calgary, Alberta, for about $650 million. Marathon said it expected to go ahead with the acquisition, which some analysts viewed as a defensive measure.

Another reason Marathon has become a takeover candidate is that it has large reserves of natural gas. Some 35 percent of its domestic reserves consist of gas that may quadruple in price as the industry is deregulated. The company also has large reserves in the British sector of the North Sea and produces 125,000 barrels of oil per day from the Yates Field in Texas. At the end of 1980, Marathon's reserves were estimated at 683 million barrels of oil and 2,100 billion cubic feet of gas. John S. Herold Inc., a Greenwich, Conn. oil appraiser , says the liquidating value of the company is about $200 a share. Mobil is offering $85 a share for 40 million shares.

Recently, Wall Street has noted these assets and concluded that Marathon was a target for takeovers. Mr. Warner of Mobil said: ''Recently we have seen large blocks of Marathon stock acquired by SEDCO and the Bass family interests. In addition, recently the number of shares traded has been abnormally large and the stock price has been highly volatile.'' SEDCO, a Texas oil driller, owns 3.9 million shares of Marathon, and the Bass Equity Enterprises, a family-owned Texas company, owns 3 million shares, along with 11 other investors.

This buying of Marathon stock, a recent issue of the Value Line Investment Survey noted, has made Marathon's stock look like a ''roller coaster.'' After the Conoco flurry, the shares dropped 20 percent. Investors bailed out after a bid for Marathon did not immediately materialize. At that point, SEDCO and the Bass family bought the shares.

Investors have also been interested in Marathon because the company's earnings have held up better than those of most other oil companies.