In the stiffest oil price rise since the Arab embargo of 1973, the Organization of Petroleum Exporting Countries decided today on a price ceiling of $23.50 a barrel as part of a confusing arrangement that will mean higher prices throughout the world.

But Saudi Arabia, the world's largest single exporter, put its new price at $18 a barrel in an apparent bid to place downward pressure on the other OPEC prices.

The Saudis, however, were as tough as the rest of the oil cartel in warning against any Western attempt to try to get a back-door price reduction by cutting the value of the U.S. dollar, the currency used to pay for most of the world's crude oil.

OPEC warned in a final communique that if the dollar continues to fall "with a view to eroding the real price of oil," the organization will convene an extraordinary conference to replace the dollar with "a basket of currencies" - a move likely to be seen as a blow at U.S. power and prestige.

In Tokyo, President Carter said OPEC's "extraordinary" price increase must be met by "a bold response" from the economic summit conference meeting there. [Details, Page A25].

The OPEC decision will have a major impact on the domestic American market, probably adding a minimum of five to six cents to the price of gasoline and heating oil.

The new prices, effective from Sunday through the end of 1979, also are expected to increase inflationary pressures and push an already weakening U.S economy toward recession.

There were fears here that the current summitt meeting in Tokyo of major industrialized countries would not produce a forceful joint action to curb oil consumption and that this in turn would lead to worldwide economic difficulties and the weakening of the dollar.

Saudi Arabian Oil Minister Zaki Yamani warned the major industrialized nations against forcing "the dollar value down in order to reduce their oil bill."

That approach, he said, "won't work, the dollar won't be a measure for our price."

Yamani said that the present fluctuations of the dollar were "all right" but that another 5 percent drop in its value would be sufficient justification to many OPEC member-states to convene the conference to get rid of the dollar as the recognized currency to pay for oil.

Yamani also laid down tough conditions for the industrialized West to swallow before OPEC will concede that it is making a meaningful oil conservation effort. He said that the West should reduce its consumption by 2 million barrels a day "immediately," a goal that had been set by the Paris-based International Energy Agency to be reached by year's end.

The Saudi added, however, that the non-Communist industrial world should also cut its consumption another 2 million barrels in 1980.

He made it clear that these cuts are to be taken from the major industrialized nations, while the world's developing countries would continue to get as much oil as ever. He said that if any developing country is cut back by the multinational oil companies, it can "call on us" and OPEC will tell the company to restore the cut or have the same amount of oil taken away from it for delivery to the country involved.

Yamani said he had already issued such orders in a few instances that had been brought to his attention.

Yamani said that it is now up to the major industrialized nations meeting in Tokyo to decide what they want to do to help themselves.

"The very high price of oil will cause a recession," he said. "So, either you will cut the consumption by your own will or by the economic forces by a recession. That's your choice."

Yamani called today's OPEC action "a compromise in a way" and said it was meant "to minimize the disorder."

There was disagreement among the OPEC ministers whether the action would eliminate the wildy chaotic spot markets centered in Rotterdam for oil that is not tied up in long-term contracts.

"I hope that the spot market will come to an end very soon," said Yamani.

Venezuelan Oil Minister Humberto Calderon-berti said that there is a "gentlemen's agreement" among OPEC members to stay out of the spot market. He estimated that about 1 million barrels a day in OPEC oil was being traded there. The main OPEC sources are known to be Iran and Iraq.

In what Yamani himself termed a "confusing and complicated" arrangement, OPEC agreed to set two separate base prices of $18 and $20 a barrel of crude oil, with a ceiling of $23.50 to include all extra charges.

According to the U.S. Department of Energy, the weighted average price of a barrel of crude in the internation market is about $18. It is difficult to say how much of a price rise today's decisions represent in real terms, except that they are clearly a major surge in most cases.

In the case of Saudi Arabia, the most moderate force in the market, the price will go from $14.55 a barrel for most of its oil to $18.

While all 13 cartel members will be charging different prices, they will fall essentially into three groups:

Saudi Arabia, the United Arab Emirates, and Qatar, will charge $18 a barrel, compared with about $12.70 at the end of 1978. Together, these three Persian Gulf states account for a third of the cartel's nearly 30 million barrels a day in exports.

Kuwait, Iraq, Iran, Venezuela, Gabon, which will charge between $20 and slightly more than $22 a barrel. These producers provide about a half of OPEC exports.

Nigeria, Algeria, Libya, Ecuador, and probably Indonesia, will charge up to $23.50 a barrel.

The net effect of the price hikes will be to increase American import costs from an average of about $18 a barrel, to more than $20 a barrel.

Many OPEC oil ministers noted that the new pricing arrangement, however disorderly it might seem, was far more disciplined than the chaos that has prevailed in the international markets since the Iranian oil shutdown in December.

I am not saying we have achieved a coherent system, but it is quite an improvement," said Algeria's Nordine Ait-Laoussine.

While Kuwait's Ali Khalifa Al Sabah pronounced himself "satisfied", Yamani said, "We did our best. I cannot say I am really happy." The Saudi said that price unity had proved to be impossible and that "huge differences" will prevail.

One of the leading U.S. oil experts, James E. Akins, the former U.S ambassador to Saudi Arabia and now a private consultant, said on the sidelines of the conference: "It's a meaningless agreement. If someone offers $24 they'll take it. Almost nothing has been decided if they keep that kind of a spread."

He called the $2-a-barrel difference between the Saudi and the general base price "a fantastic bonus" for the four U.S. major oil companies that operate in Saudi Arabia, implying that savings are unlikely to be passed on to consumers.

Sharp reaction to the OPEC price hike came quickly in Europe.

French Prime Imister Raymond Barre said the price will cost oil-import dependent France an additional $4.4 billion this year.Further, Barre said, the higher oil price will force France to forego its pledge to hold inflation down to 10 percent this year.

The increase will also have a massive impact on U.S. domestic oil prices. Since only 40 percent of U.S. oil is under domestic oil price controls, the domestic oil industry is expected to raise its prices in step with OPEC.

A semi-official Italian estimate was that the new prices would cost Italy $3.6 billion more for oil imports this year.

Last week, U.S. Energy Secretary James Schlesinger had estimated that the U.S. import bill next year would rise to $60 billion, from $52 billion this year. But today's unexpectedly high increase could mean that the United States will have to pay $60 billion in the current year.

Extrapolating from U.S. government estimates before today's announcement, the oil price increases are expected to raise the consumer price index three to four points.

In an obvious attempt to prevent oil prices from rising even more this year, Yamani refused to accept a new price-setting OPEC conference before December.A number of other countries, including Libya and Venezuela, had called for a conference in September.

Asked how much today's price rises would cost Western consumers, Yamani said it would be difficult to tell but that for those "fortunate enough" to get most of their oil from Saudi Arabia or the United Arab Emirates, the weighted average would probably be about $19 or $20 and considerably higher if the oil comes from elsewhere. Imports from the lower-priced OPEC producers make up about a quarter of the U.S. oil purchases abroad.

Yamani was cautious about whether Saudi Arabia, the only country in a position to provide enough new production rapidly to influence the world supply and demand picture all by itself, would raise its oil output to ease the situation. Referring to Saudi plans to raise productive capacity to 14 million barrels a day from the present 11 million barrels daily, he said there is no schedule to complete the new capacity.

Saudi Arabia now produces 8.5 million barrels a day.

Venezuela's Calderon-berti said that he had been told during the conference that the Saudis might raise their output by another 1 million barrels a day. CAPTION: Chart, OPEC Benchmark Prices, 1970-1979, By Dave Cook - The Washington Post