The Environmental Protection Agency and the Department of Energy are negotiating in an attempt to head off an administrative duel over gasoline decontrol proposals.

EPA officials are concerned that if the DOE implements certain gasoline decontrol plans, the spread between the price of leaded and unleaded gas will grow, and thousands of motorists will resort to using the much cheaper leaded fuel.

Under such a scenario, EPA officials contend, emission control systems in cars will be neutralized, and the result could be a deteriorating air quality because leaded gasoline is dirtier than unleaded gasoline.

The latest round of a continuing battle over this issue between the two agencies was a recent threat by the EPA to challenge the environmental impact statement (EIS) DOE used to justify gas decontrol measures.

The EPA had until yesterday to refer the matter to the Council on Environmental Quality. The council, under the Clean Air Act, has the authority to force DOE to do another impact statement before issuing the decontrol regulations.

After negotiating with DOE late yesterday, however, the EPA was granted a five-day deadline extension in an effort to work out a compromise with DOE.

EPA officials said yesterday they were optimistic that a compromise could be reached.

Such a compromise would involve a price monitoring system that would let the government know if the difference in price between leaded and unleaded gasoline was growing to dangerous proportions.

If the spread became artificially high, automatic regulatory price controls would be imposed.

Officials of the two agencies are now trying to determine the actual difference in the cost of producing leaded and unleaded gasoline, estimated to be in the range of 2 to 3 cents per gallon. EPA sources claim that the price difference at the pump, however, has gone as high as 10 cents per gallon in some areas.

Meanwhile, in a letter sent yesterday to David Bardin, head of the DOE Economic Regulatory Administration, consumer advocate Clarence Ditlow, head of the Center for Auto Safety, accused the department of ignoring EPA's fears.

Ditlow pointed out to Bardin that it was EPA's role to question EIS statements. "[DOE] efforts to mold EPA's decision flagrantly violate the separation of functions Congress so carefully created in the Clean Air Act," he said.