President Clinton today will unveil tough new environmental rules that will require oil companies to produce cleaner gasolines and force automakers, for the first time, to develop sport-utility vehicles (SUVs) that meet the same stringent emissions standards as cars.

These final rules, to be issued by the Environmental Protection Agency, will sharply reduce the level of gasoline sulphur, which can clog catalytic converters designed to reduce pollutants. Environmentalists say the changes, which will begin in 2004, will have as profound an effect on the kinds of gasolines available as did the phaseout of leaded gasoline, which began in the early 1970s and ultimately led to complete elimination of that fuel from the United States.

The newer gasolines could be used in older cars and trucks without any modifications. But oil companies, which have fought the proposal, have estimated that cleaning up fuels could add as much as 5 cents to 6 cents to the cost of a gallon of gasoline.

Bob Slaughter, general counsel for the Washington-based National Petrochemicals and Refiners Association, said the clean-gas rules being announced today actually amount to a 90 percent reduction in the amount of sulphur in gasoline.

"Our members tell us that probably every refinery is going to have to make a significant investment to do this," Slaughter said.

The new emissions rules will apply to all "light trucks"--pickups, minivans, vans and sport-utility vehicles. However, in writing the final version, the EPA also strengthened the rules to apply to the heaviest passenger trucks as well.

The truck rules could limit the weight of the biggest light trucks to 8,500 pounds, a heavyweight status reached only by a few of today's trucks, such as specially equipped versions of Ford Motor Co.'s Excursion sport-utility vehicle.

Currently federal regulations allow most trucks and sport-utility vehicles to escape tougher emissions standards. By forcing the heavier trucks to meet car clean-air standards, the government hopes to keep a lid on the growth of super-heavy sport-utility models, some Clinton administration and auto industry sources said yesterday.

Taken altogether, the new rules amount to a "clean-air trifecta that will cut harmful smog, reduce fine sooty particles breathed deep into the lungs and help curb air pollution damage to our forests, lakes and streams," said Vickie Patton, a Washington, D.C., attorney for the Environmental Defense Fund.

Implementing the new federal clean-gas rules would be the equivalent of taking 54 million cars off the road, advocates of the measure have said.

For years automakers have been arguing that the only way they can produce more low-pollution engines, as well as improve fuel efficiency, is with the help of the nation's petroleum industry.

Most current U.S. gasolines average a sulphur content of 300 parts per million. Sulphur, a fuel additive, fouls emissions control devices, such as catalytic converters, which are designed to burn off pollutants leaving tailpipes. Sulphur also upsets emissions control sensors, such as Onboard Diagnostic II systems, installed in many new cars and trucks.

The automakers wanted a sulphur content standard of zero parts per million. Petroleum makers balked, saying that reaching that standard would be prohibitively expensive, especially for smaller refiners.

A compromise was reached after several years of wrangling. The new, average 30-ppm standard will apply in all states except California, which has mandated a sulphur content of 15 ppm.

Earlier this year, oil refiners estimated that the shift to clean gas would cost them $5 billion to $6 billion in new processes and tools.

Also affected by the new rules, which were first offered as proposals in May, are diesel-powered vehicles, which eventually will have to meet gasoline-engine, clean-air standards.

Diesels generally emit sooty, thin particulate matter that can cause or aggravate respiratory problems.

However, all major automakers now are developing and, in some cases, producing a new generation of what they call fuel-efficient, clean-burning diesels.

William Noack, GM's top Washington spokesman, said his company will do what is necessary to met the EPA mandates. "It's not going to be easy, and it's going to be very expensive. But we're putting programs in place, now," Noack said.

Similar comments came from GM's top rival, Ford Motor Co.

Clean-gasoline rules will begin phase-in by 2004 and will begin a year later for smaller refiners. Trucks will have to meet the same clean-air standards as cars by 2009, sources said.

The president will make his announcement in Washington this afternoon at Maury Elementary School in the 1200 block of Constitution Ave. NE. According to government and industry sources, the president will link his administration's latest clean-air initiative to the future health of the nation's children--whom the president will describe as the nation's future.