Mobil Corp., the nation's second-largest petroleum company and a major new corporate resident of metropolitan Washington, made its first presentation to local securities analysts last week since moving its U.S. marketing and refining headquarters to Fairfax County from mid-Manhattan.

Allan Murray, president of the firm's worldwide marketing and refining operations, took the occasion to express his personal support of President Reagan's proposal to eliminate federal grants to corporations for synthetic-fuel projects.

"The man who is going to make the money ought to lose it," he told the Washington Society of Investment Analysts. Murray emphasized his view that synthetic fuels must be developed as part of an overall national strategy for future energy resources. But the role of government should be limited to initial, pure research, he added.

"I do believe, however, that it would be a mistake for this nation to get involved with any financing when you get beyond the research stage . . . What's going to happen is if I have a good idea, I'm going to do it myself; if I have a lousy idea, I'm going to get the government to finance it so I don't lose any money," Murray told the analysts.

Under the Reagan administration's reordering of the budget and proposed spending cuts, Department of Energy synfuels grants would be eliminated after fiscal 1982, and the new Synthetic Fuels Corp. is supposed to emphasize development by the private sector instead of government for a savings of $2.7 billion of fiscal 1986.

Murray said the only exception should be government guarantees against sudden price decisions by the oil-producing countries, designed to drive a synthetic fuels operation out of business.

Mobil, which also owns the depressed Montgomery Ward retail chain, currently has more than 1,000 employes in the Washington area after moving its U.S. headquarters here last year. Murray heads the domestic operation as well as the firm's overseas refining arm, from offices in New York.

"They love it here," Murray said of the new Mobil residents in metropolitan Washington.

In answer to a question, Murray said emphatically that Mobil has no intention of unloading its Montgomery Ward retail chain, which reported a loss of $133 million last year. He said Ward will move to centralized checkouts in some stores and close unprofitable units but that the retailer "is basically strong."

Ward was hurt more severely during last year's recession than some other large retailers because its ratio of credit sales is higher, and its borrowing had more short-term maturities than competitors. As interest rates hit record levels, Ward's profitability from credit operations was pinched sharply.