IT ALL seems so long ago. But if you think very hard you might remember multi-hour gas lines, odd and even days, and perhaps a siphon burn or two. Those were just a few of the facts of life of the mid-1970s oil crust that gave a real fright to Americans, forcing them to insulate their homes, sell their Cadillacs and pay attention to a faraway group of Arab nations.

But with the stabilization of oil prices and disarray of the Organization of Petroleum Exporting Countries (OPEC) came a return to complacency. Americans are in the process of forgetting all they learned about energy conservation. Yet convincing signs--including a recently released repot by the International Energy Agency (IEA) indicate that a new oil crisis may develop by the end of the decade that would "deal a devastating blow" to major industrialized countries.

Officials at the 21-nation energy agency claim that the global recession has the decisive factor in lower gas prices. Put simply, they say, poor economic growth caused a reduction in energy demand. But UIf Lantzke, executive director of the agency, has predicted that the recession must inevitably come to an end, hence causing a sharp increase in gas prices.

"If average annual economic growth in industrialized countries remains around two percent for the next decade, I would agree energy probably will not be a big problem for the rest of the decade," states Lantzke. "But I doubt any democratic society could accept the increasing unemployment such slow growth would entail."

According to the agency report, oil production in the Unite States, the North Sea and the USSR will stagnate by the late 1980s and even OPEC output will drop due to "declining reserves in some countries and political decisions in others." At the same time, the energy needs of Third World countries will increase dramatically thanks to economic development, increasing urbanization and industrialization. So a large group will be fighting for a smaller pie.

But the world energy market is "likely to remain deceptively stable through the mid-1980s." the IEA report says. And therein lies the danger, for people and governments will begin once more to neglect the energy issue and ignore pleas for continued conservation. True, gains have been made that will not easily be reversed. No one, for example, is about to rip insulation from walls or trade-in a fuel efficient compact for an oversized gas guzzler. But efforts to find alternative energy sources will diminish and conservation policies in general will take on less urgency.

By the end of the decade, world wide demand for oil could top supply by as much as nine million barrels per day, the IEA report concludes. It is not difficult to imagine the resulting escalation of international tension as countries scramble to obtain their energy needs. Nor is it hard to foresee the internal chaos another oil shortage will wreak on an unprepared nation. Soon the energy scare of the 70s may seem a mild prologue to the real crisis.