Don't let the mournful cries of the banks and the oil companies fool you: the collapse of the OPEC oil cartel, which promises lower prices not only for OPEC oil, but for domestic oil as well as other energy sources, is good news for America, and for depressed economies all over the world.

Some banks, and some producing countries that unwisely bet oil prices would go up forever will be hurt, as they should be for making bad business decisions. The oil companies that gleefully rubbed hands with each new OPEC increase in the 1970s will see shrunken profits.

But lower oil prices will be a tonic for rich and poor oil-using nations alike that have been driven into a depression by a greedy cartel.

It is ironic that many observers, who are painfully aware of the devastating effects of the two massive oil price "shocks" in the 1970s, now brood over the prospect of a sharp price decline. The well-known New York oil analyst, Walter Levy is widely quoted as saying that if oil drops from the present $34-a-barrel OPEC monopoly level to $20, it would trigger a "disaster" for Mexico and other countries heavily in debt, because their oil revenue will slide.

The $34 monopoly price has prevailed since October 1981, despite the enormous oversupply of oil. And no one in the United States government ever criticized the "moderate" Saudis for their role in maintaining an artificial price structure that has raised veritable hell with the world's economy.

In the aftermath of OPEC's disarray and a bitter fight for market shares between the Saudis and Iran on one hand, and the Saudis and African producers on the other, it isn't yet clear how sharp the oil price decline will be.

But it is certain that the price is headed down, as was inevitable in the face of a massive glut. Compared to the $34 "benchmark," the spot market price fell on Monday to $29.75, following the collapse of OPEC's effort to establish new production quotas and prices.

"Perhaps some bank loans to oil-producing countries like Mexico will go bad, or have to be refinanced as the price falls," says Washington oil consultant Joseph Lerner. "On the other hand, most oil-importer borrowers like Brazil are also in financial difficulties, and their ability to pay back loans will improve. Bail out the bankers who school everyone in financial prudence? Poor policy: the oil glut 'signal' has been clanging for a long time. But anti-competitive producers managed to sustain prices."

As to Levy's fear of disaster from a dramatic price break, Lerner recalls that OPEC's 1979 increase was $12.66 a barrel, or nearly 95 percent. A reduction of $14 to a $20 level would be on the order of 41 percent. "Must prices go up like a rocket and decrease like a glider?" Lerner asks.

Oil analyst Lawrence Goldmuntz of Washington cites estimates that OPEC's monopoly pricing has caused 25 to 30 percent of the unemployment in the industrial countries. And, according to the IMF, oil price increases are a major cause of the build-up of Third World debt estimated at an oppressive $500 billion.

So there is reason to cheer, rather than fear, lower oil prices. Economist Walter Heller observes that "a sick U.S. economy would get just the tonic the doctor ordered: the equivalent of a $50 billion excise tax cut that would unleash consumer spendkng (and) boost business profits.." And a price drop, provides an incentive to continue filling the Strategic Petroleum Reserve.

The significant thing to remember is that the oil glut is not merely the result of declining demand at a time of world recession. The primary reason for the glut is that OPEC's pricing policy forced the consuming world to learn three things: first, how to conserve on oil use; second, how to find new sources of oil outside of OPEC; and finally, how to find other fuels to substitute for oil.

The cartel set the stage its own destruction by pricing oil out of the market, as professor Arlon R. Tussing of the University of Alaska writes in the winter 1983 Public Interest. Already, demand for OPEC oil has slid from the peak of 31 million barrels a day in 1979 to 17 million barrels a day. And if there weren't some OPEC members already discounting-- that is, cheating on the cartel price-fixing agreement--OPEC sales would be even less.

Tussing sees "the most stable and easily sustainable price range" in the future as $10 to $18 a barrel.

Western leaders copped out in the 1970s when they let OPEC get away with owtrageous price increases. They would make another enormous error if they are encouraged by banking, oil or other self- interest groups to do anything except let nature take its course. This is a moment to cherish and enjoy.