As Nigerians begins a five-week process of electing their civilian government in 13 years, other nations, particularly those in the industrial world, are waiting to see what direction this country's oil policy will take.

Nigeria produces about 2.5 million barrels of high-quality crude oil a day, and the relatively young military rulers have already used the oil as a lever to influence the oil-hungry West's policies toward white-ruled South Africa, Nambilia (Southwest Africa), and the controversial new government of Zimbabwe-Rhodesia.

For example, the implicit Nigerian threat of an oil cutoff, couched in the diplomatically vague terms of "appropriate response," is said to have influenced President Carter's decision not to lift economic sanctions against the Salisbury government of Prime Minister Abel Muzorewa, according to one Western diplomat.

Nigeria supplies 15 percent of U.S. oil consumption and any cutoff of oil or disruption in the flow of crude to the United States would affect seriously America's current energy woes.

The Nigerians already have put teeth in their "appropriate response" warning in May by excluding British companies from biding on a $200 million port construction contract for which the British had supplied the financing. Lagos made it clear that it was reacting to Conservative Prime Minister Margaret Thatcher's reported intention to lift sanctions against Salisbury.

"The Nigerians have made it very clear that there would be serious implications" for U.S.-Nigerian relations if sanctions against Zimbabwe-Rhodesia are lifted, U.S. Ambassador Donald Easum said.

"But they have not specially said they will cut off our supply," he said. "It's an open question if manipulation would give them the desired results."

Nigeria has shown in two other recent cases that it is willing to use oil as a political weapon. First, it reduced British Petroleum's allocation by 25 percent because that company allegedly sent a South African taker to Nigeria to collect oil.

Lagos also stopped shipments of oil to Ghana to protest that West African nations's executions of three former military heads of state and other high-ranking officers.

It is unclear to what degree a new civilian government is likely to change Nigeria's present policy. All four presidential candidates have been vague on foreign policy questions, which in Nigeria are inseparable from the oil issue.

Of course, if a new civilian government is unable to provide stable rule to Nigeria, the implications could be severe both for the industrialized nations and for this country's own developing economy.

Bolaji Akinyemi, director of the Nigerian Institute of International Affairs, a government foreign-policy think tank, said Nigeria's foreign policy probably "will be slowed by domestic pressures" and the political need to respond to agitation for higher wages in an inflationary economy, expanded health services and more schools.

Other influential Nigerians, such as Ashland Oil Co. executive Esom Alintah, are not so sure that a civilian government will take a conservative turn, even though most candidates favored in the election are older and British-trained.

"The institutions and policies set up by the military government cannot be wiped away overnightr," Alintah said."Those [makers of foreign policy] that will be replaced will be replaced by younger, more radical people."

Alintah indicated that Nigeria will be willing to continue using the oil weapon to influence events in southern Africa, despite any potential adverse economic effects.

"Many Nigerians feel there is no calculation you can put on race, whether you lose money or not," he said.

In a blunt speech, Army chief of staff Theophilus Danjuma castigated Nigerian foreign policy under its first civilian government as "timid and rudderless" and said it would be a "fallacy" for foreign governments to think that the incoming civilian government will be more "pliable" than the military government has been.

"Indeed if anything the country will become more and more radical as the years go by and as young men and women who are unencumbered by colonial influences take over," Dajuma said.