The District of Columbia buys gasoline at a price that is up 20 cents a gallon more than the base price its residents pay at their neighborhood pumps, a D.C. City Council hearing disclosed yesterday. The difference adds up to hundreds of thousands of extra dollars that the city has to pay to run its fleet of cars.

In addition, the District pays 18 cents more a gallon than Fairfax County does, 11 cents more than Montgomery County and four cents more than the federal government to buy a gallon of unleaded gasoline.

Kenneth E. Quinlan, head of purchasing for the D.C. General Services Department, said the higher price paid by the city results from the federal gasoling allocation program now in effect because the of nationwide gasoline shortage. Under the program, bulk gasoline customers, are locked into reveiving gasoline from their previous "supplier of record."

In the District's case, this means buying from Roarda Inc., a wholesale "middleman" distributor based in Bel Air, Md., north of Baltimore. Because Roarda is a middleman, its price is higher than the price of major oil companies -- chiefly Gulf -- whose products it distributes. By contrast, Fairfax and Montgomery counties get a better deal because they buy their gasoline straight from Gulf, without going through a a middleman, county officials said.

Quinlan said the city currently pays $1.13 1/2 a gallon without District or federal gasoline taxes -- the equivalent of $1.27 1/2 if taxes were added.

The current average self-service pump price for unleaded gas in the Washington area is $1.24 1/2, including taxes, according to the American Automobile Association. The Lundberg Letter, the nation's leading petroleum marketing publication, said its most recent price survey last month showed an average in the region of $1.21 1/2 a gallon.

Council member David A. Clarke (D-Ward 1), who testified at yesterday's hearing by the council's Judicary Committee, said the price at BP station in his ward, at Fifth and U streets NW is $1.07, taxes included. He said he was told that figure includes a required three-cent rollback to make up for past overcharges by the refiner.

The city "would do better to go down to the [private] gas station" to buy its fuel, Clarke declared. "I think it's outrageous that . . . this city is buying gas . . . at a price higher than the people are paying at the pump."

Quinlan said the city annually buys about 3.7 million gallons of unleaded gasoline and nearly 1.5 million gallons of other grades.

Clarke estimated the city must pay between $220,000 and more than $500,000 extra a year for gasoline, depending on which price comparison is used.

Where the District pays $1.13 1/2 a gallon for unleaded gasoline, Fairfax County pays 95 cents a gallon, Montgomery County, just under $1.02, and the U.S. General Services Administration, $1.09. Fairfax County's price is so low, a county official said, because the county sends its own tank trucks to the refiner's distribution center, while the other jurisdictions receive deliveries.

If the city can appeal to get a different supplier and has not done so, Clarke told Quinlan, "I consider that an extreme act of dereliction." Quinlan said no appeal has been made, and promised to find out whether the city could file one.

Clarke told Police Chief Burtell M. Jefferson, who was testifying on a supplemental budget request, that he may recommend that the police department's gasoline budget be cut.

"Please don't penalize me for a situation I have no control over," Jefferson pleaded, his voice trembling. He said such a move would force him to reduce the number of patrol cars on the streets with increased danger to citizens. The department already has ordered policemen to park their patrol cars for one hour each shift and walk their beats instead.

Yesterday's hearing was on portions of Mayor Marion Barry's proposal for $62 million in supplemental congressional appropriations for the city, a component of his plan to reduce a budget deficit that could run as high as $172 million.

Witnesses also appeared from the city's Corrections Department, which faces layoffs of 360 employes as part of the mayor's cost-cutting proposal But they were told by Carke to limit their testimony to the request for $6.8 million in supplemental funds for mandatory cost increases, rather than the mayor's proposed reductions. Clarke said that, in his opinion, Barry has the legal right to cut city budget allocations in the face of deficit without council approval.

Earlier yesterday, a group called the Coalition for Financial Accountability -- made up of community organizations, welfare rights activists and some government employes -- called on the mayor to balance the budget without cutting city services or laying off workers.

Coalition spokesman Mark Looney said the mayor should instead impose a tax on the gross receipts of businesses and tighten tax collection procedures.

In a related development, Council Chairman Arrington Dixon criticized the mayor for not telling the council that the city needs this month's $17 million federal payment two weeks early in order to pay its current bills.

Barry had briefed the council on Monday on the city's financial crisis.