Officials at the National Highway Traffic Safety Administration are preparing for hearings that promise to be as hot and sticky as the steamy days of August.

At issue is the NHTSA's tentative decision July 18 to lower the corporate average fuel economy (CAFE) standard from 27.5 miles per gallon to 26 mpg for the 1986 model year.

The proposed one-year rollback does not please the auto makers it was supposed to help. Nor does it quiet the supporters of the standard it was designed to mollify. Representatives of both sides have filled the mails with news releases and other missives outlining their objections to the NHTSA's decision, which is scheduled to be the subject of hearings here on Aug. 8 and 9.

The CAFE standards were established in 1975 in response to the gasoline shortages spawned by Arab oil embargoes. The law requires the NHTSA to establish an average "maximum feasible" fuel economy level for all new-car fleets sold in the United States.

Manufacturers that fail to meet the CAFE standard are fined $5 for each tenth of a mile they fall below the limit. That fine is then multiplied by each car in their new-car fleet, regardless of whether individual vehicles meet the standard.

The U.S. fleets of General Motors Corp., Ford Motor Co. and a number of European car manufacturers do not now meet the current CAFE standard. They say the system unfairly penalizes them for trying to fulfill Americans' demand for large cars.

Some of the firms have asked the NHTSA to lower the CAFE standard to 26 mpg for an indefinite period. Others have asked for a respite of at least three years. All were upset by the NHTSA's proposed one-year reduction and are arguing their case through a Washington-based group called AutoChoice.

"The adjustment for only one year continues the threat to U.S. auto worker jobs, manufacturers and American consumers," said Jeffrey B. Conley, AutoChoice executive director. "A one-year adjustment does not provide the needed relief and creates uncertainty that will make it extremely difficult for U.S. car makers to develop plans to meet the standards," Conley said.

Not so, said Lee A. Iacocca, chairman of Chrysler Corp., which has long opposed relaxing the standard. "The whole country was held hostage" by Arab oil-producing nations in the 1970s, Iacocca said. "Now, we're setting ourselves up to be hostage again in the 1990s" by relaxing fuel economy standards, he said.

The Chrysler chief said he's all for consumer choice, as long as the public is willing to pay for freedom of selection. "If you're going to have the privilege of driving big cars, you should pay for it," Iacocca said.

But some NHTSA sources contend that Iacocca is practicing the piety of convenience. GM, Ford and Chrysler compete directly in nine auto-weight classes set up by the Environmental Protection Agency, those sources say. GM has the highest fuel economy rating in four classes, Ford has the highest in three, Chrysler leads in one, and GM and Chrysler are tied in one, according to the NHTSA sources.

"Chrysler has said that it is the fuel-economy leader. But when you look at the categories in which the three companies compete head-to-head, Chrysler is no more technologically advanced in fuel economy than GM or Ford," one of the NHTSA sources said.

Officials at the three companies agree that they are direct competitors in nine weight classes. But beyond that the matter is as hazy as Washington's summer. "Who the hell walks into a dealer showroom and orders a car by weight?" one Chrysler man remarked.

The fact is, according to the Chrysler official, that his company has spent billions of dollars reducing the overall weight and improving the overall fuel efficiency of its new-car fleet. People are buying what Chrysler makes, and that's why Chrysler is meeting the standard, the official said.