The much talked about world oil glut has US motorists smiling all the way to the gas pump.
But some experts are concerned that the push to conserve and the shift to alternative energy sources - both of which helped make the glut possible - may now sputter and stall.
''We've hit a low in conservation because oil prices have stabilized,'' says Dr. Martin J. Bernard, director of the Center for Transportation Studies at the Argonne -National Laboratory near Chicago. But, he adds, ''it's very important not to swing back'' to old consumption patterns.
For now, however, concern about the pace at which the United States is weaning itself away from heavy dependence on imported oil is being overshadowed, to some extent, by cautiously optimistic reports about future world oil prices.
Conoco Inc., in a recently published report entitled ''World Energy Outlook Through 2000,'' says that during ''the next several years'' world oil prices may rise no faster than the rate of inflation. During the remainder of the 20th century, the report says, price increases are likely to average 2 to 3 percent a year above the rate of inflation.
One New York investment firm's petroleum industry analyst forecasts that world oil price increases will not keep pace with inflation, at least through 1985. He expects, therefore, a ''modest'' drop in the ''real''(inflation adjusted) price of oil through 1985.
William M. Brown, director of energy studies at the Hudson Institute, has predicted that members of the Organization of Petroleum Exporting Countries (OPEC) will undercut each other's prices as they scramble to boost their share of a world market awash in crude oil. He says this could result in the price of OPEC oil dropping from the current $34 a barrel to $24 a barrel (in 1981 dollars) by 1985 - a 30 percent reduction in real terms.
To differing degrees, these forecasts are based on slowing growth in demand for energy, more efficient use of energy, a shift toward other energy sources, and a reduced dependence on OPEC oil.
But these price forecasts carry a commom warning: If there is a major supply disruption, throw them in the wastebasket.
And there's the rub. Reports from the Persian Gulf, for instance, are talking about the increased tempo in the war between Iran and Iraq, the fact that several Mideast countries are poised to get involved, and the threat this may pose to Persian Gulf oil supplies.
''There's a high probability of a significant crisis in the Middle East within this decade, or by the turn of the century - especially without (the late Egyptian President Anwar) Sadat,'' says Dr. Bernard. ''Given that, if you have a 'lean' system, you can cope better with shortages. The best contingency measure is long-term conservation.''
That Americans can conserve is evident.
''The US is consuming between 15 and 16 million barrels of oil a day - about one-third of the free world's consumption. That's down from around 18 million barrels a day in 1977,'' says Michael Canes, director of policy analysis for the American Petroleum Institute (API).
Between 1977 and 1981 crude oil imports have fallen 36 percent - from 6.6 million barrels a day to roughly 4.2 million barrels a day, according to API.
According the Motor Vehicles Manufacturers Association, the fuel efficiency of all the cars on the road has risen from a 20-year low of 13.1 miles per gallon in 1973 to 15.2 miles per gallon in 1980, the last year for which they had figures. As for the new car fleet, in 1974 it averaged 14.2 miles per gallon , according to association data. In 1981 that rose to 25.2 miles per gallon.
And a recently completed preliminary US Department of Energy (DOE) study of energy use in residential and commercial buildings found that consumption per household dropped from 226 million BTUs in 1973 to 208 million BTUs for 1980. For commercial buildings, consumption declined from 430,000 BTUs per square foot in 1973 to 400,000 BTUs per square foot in 1980.
''We are seeing significant progress in conservation,'' says DOE analyst Peter Back. ''But it's nowhere near what we could be doing.''
But along with this progress, some energy experts see signs that falling gasoline prices are reawakening old consumption habits among Americans. Dr. Bernard says, ''The Japanese are upsizing their cars, and there's a slight comeback in the big-car market. The conservation ethic goes quick in a glut.''
The comeback in big cars he referred to was evidenced in a report from Detroit last week. It notes that thus far in the 1982 model year, large and luxury cars accounted for 18.5 percent of all new cars sold. This compares with 16.8 percent for the same period in 1981.
Says one Wall Street oil industry analyst, ''Declining demand is in direct relation to price increases . . . . Now, with the expectation of flat gasoline prices, we may on the verge of putting ourselves in the long-term position of increasing our dependence on OPEC. That's just what -happened after the oil embargo and price shock of 1973-74.''
It's this historical pattern of increased consumption after an initial price shock that adds to experts' concern. According to API figures, oil imports rose from 3.2 million barrels a day in 1973 to 6.6 million barrels a day in 1977. Statistics from the DOE show that gasoline consumption dropped slightly between 1973 and 1974 - from 6.7 million barrels a day to 6.5 million barrels a day. But in 1975 gasoline consumption resumed its increase to a 1978 peak of 7.4 million barrels a day.
Conservation is not the only activity affected by softening oil prices. Like conservation, oil industry experts say, the alternative energy business is tied to the current price of oil and to expectations of future prices.
''If energy prices stay stable or decline in real terms, there is no incentive for oil companies to develop more expensive alternatives,'' says Dr. Bernard.
Exxon announced last week that it was scaling back its synfuels program. Other firms have been reducing their participation in tar sand development in Canada.
While these developments bear watching, experts say, it still may take another year or two to see if the current glut has sidetracked America's move toward long-term conservation.