Four Washington area men were indicted yesterday by a federal grand jury in Baltimore on charges growing from an an alleged automobile odometer rollback scheme that FBI officials said involved more than 1,000 used cars sold to local consumers since 1981.

Officials estimated that the fraud cost consumers an estimated $500 to $1,000 for each odometer rollback, or a total of about $500,000, because the value of the automobiles was inflated.

Charged in the 34-count indictment were: Walter Robert Dickson, 63, of Silver Spring; his son, Douglas Craig Dickson, 39, of Frederick; Haynes Lee Locklear, 74, owner of Riggs Motors, a wholesale and retail used car dealership in Hyattsville, and Carl Raymond Wells, 53, owner of S&W Auto Sales on Rhode Island Avenue NW.

The elder Dickson and Locklear were arrested last week by FBI agents and charged with using the U.S. mail in a scheme to defraud consumers by selling used automobiles with odometers that falsely reflected lower mileages. Both men were released on $25,000 bonds after appearing before a U.S. magistrate.

The indictment accuses all four men of mail fraud. In addition, the Dicksons are charged with failure to furnish the correct mileage statement in connection with the transfer of a motor vehicle. Locklear is charged with failure to retain complete written mileage disclosure statements in connection with the transfer of motor vehicles.

FBI agents began an investigation of odometer tampering in the Washington area more than a year ago, in cooperation with officials of the Maryland and Virginia departments of motor vehicles, according to an affidavit filed in federal court.

The affidavit, signed by Special Agent Stanley J. Orenstein, said that Locklear, trading as Riggs Motors obtained more than 1,000 used automobiles wholesale from new car dealers in Maryland, Virginia and North Carolina since 1981. Riggs then reassigned the cars to the Dicksons, either directly or through Wells' Washington firm, the affidavit said.

The Dicksons, who were not licensed car dealers, retitled the cars in Virginia and sold them as their own to consumers in this area by placing personal classified ads in newspapers, the FBI said.

"There would be a telephone number in the ad and the reader would be asked to respond to the phone number," the FBI said. "That number would be to Walter Robert Dickson's number in Silver Spring or to Douglas Craig Dickson's number in Frederick . . . or to the telephone number of a surrogate appointed to sell on behalf of Douglas Dickson."

The affidavit said that the cars sold by the Dicksons showed mileage that was 15,000 to 80,000 miles below their true mileage. The mileage on the cars and on the car title work was falsely reduced to inflate the value of the cars, the affidavit said.

One case cited in the affidavit involved a 1978 Cadilac that had 98,256 miles when it was traded by its original owner to a Greenbelt dealership on June 21, 1983.

The Cadillac subsequently was sold to S&W Auto Sales, the FBI said. By the time the title passed to Walter Dickson, the mileage was 43,140, the affidavit aid. Dickson then sold the car to a Silver Spring consumer, falsey stating that he had purchased the Cadillac new, the FBI said.