A congressional analysis of the government's purchases of crude oil for the Strategic Petroleum Reserve--the stockpile that would be used to alleviate shortages in a new oil crisis--concludes that federal buyers pay "consistently and significantly higher" prices for foreign oil than the major oil companies do.

A House Government Operations subcommittee said that in the 22-month period that ended Sept. 30, the government "would have saved $1.56 billion in procurement costs if it had purchased oil each month at the lowest price paid by a private U.S. oil company importing oil from the same countries."

The subcommittee staff said the government, which paid an average of $35.43 per barrel for oil during that period, could have saved $11.08 per barrel if, in each case, it had bought the oil at the lowest price being paid to the foreign supplier that month by the major oil companies.

"We understand that it is unrealistic to think that the government can consistently buy crude at the lowest price it is sold to any trader," said Peter S. Barash, staff director of the subcommittee. "But the federal government should be getting a price comparable to what private oil companies are paying."

Subcommittee chairman Benjamin S. Rosenthal (D-N.Y.) sent a copy of the staff analysis to the General Accounting Office yesterday and asked for an investigation of "the reasons for these apparent excessive payments . . . . "

Rosenthal said he was particularly concerned by the staff's finding that the government's purchasing practices appeared to be getting worse.

He said that, for the first nine months of 1981, 62 percent of the purchases by private oil companies were at a better price than that obtained by the federal government. For the first nine months of 1982, he said, the figure was 64 percent.

"In the month of March, 1982, the U.S. government paid more per barrel than every single private company purchasing oil from the same country," Rosenthal said.

"That was almost $200 million of the U.S. taxpayers' money unnecessarily spent for just one month's purchases . . . . "

Rosenthal said that, because the U.S. government -- which already has stockpiled more than 285 million barrels of oil in salt domes along the Gulf coast of Louisiana and Texas -- will be purchasing an additional 450 million barrels, "it is essential that excessive costs be avoided."

Richard D. Furiga, the deputy assistant secretary of energy in charge of the Strategic Petroleum Reserve, yesterday expressed surprise at the study's conclusion that the government was paying too much for oil for the stockpile.

"Our own analyses have shown that the Defense Fuel Supply Center, which purchases most of the oil for the reserve, is getting it at very, very competitive prices," Furiga said.

Col. Thomas Olofson, the Air Force officer who runs the supply center's purchasing program, could not be reached for comment.

A General Accounting Office analyst, however, said it "would not surprise me terribly to find that private companies are getting a better price.

"I assume most major oil companies have long-term contracts with their suppliers, and they would presumably get a better price than the government, which primarily buys from traders or intermediaries on the spot market," the GAO analyst said.

"The Defense Fuel Supply Center has gone out a couple of times looking for long-term contracts, but to date they haven't been terribly successful."

The subcommittee staff performed the analysis by examining U.S. Customs Service reports that list monthly crude oil imports for each purchaser by country of origin, quantity and prices paid, excluding transportation costs.

During the 22-month period analyzed by the staff, 140.7 million barrels of crude oil were imported for the Strategic Petroleum Reserve; private oil firms imported 2.9 billion barrels of oil, according to the Customs records.

The staff study said that in February, 1982, for example, nine companies imported crude from Britain at prices below the price paid by the reserve, with only one private firm paying more.