Consumer specialist George Rose calls them "revenue enhancers" and says they can raise the price of a new car sold in the Washington metropolitan area by $3,000 to $5,000.

The revenue enhancers, according to Rose, typically are dealer-added options that are sold at inflated prices in order to increase dealer profit.

"Dealers can charge what they want for profit," said Rose. "But they have found that there is less consumer resistance to paying for an additional option than for additional markup, so they load up a car with options and tell the consumer to take the car as it is or leave it," said Rose, who is director of the automobile section in the Montgomery County Office of Consumer Affairs.

Examples of revenue enhancers, he said, include:

* Protection packages that include rustproofing, paint protection, undercoating and perhaps door guards and body side molding. Rustproofing, for instance, normally costs a dealer $50, but may be sold to the car buyer for $400 to $800.

* Mandatory floor mats that may cost the dealer $10 but which he sells to the car buyer for $100 to $150.

* Dealer-installed AM/FM radio with cassette player that go for $300 to $400 but which a consumer could purchase elsewhere for $100 to $150.

* Extended warranties that the dealer may purchase from the warranty company for $150 to $200 and then retail to the consumer for $800 to $900.

* Theft protection packages that can include anything from an alarm system to a program in which the vehicle identification number is etched onto the glass windows and windshield.

Don Beyer, a Falls Church car dealer and chairman of the advertising committee of the Automotive Trade Association of the National Capital Area, a trade group representing local dealers, said that a dealer with a limited supply of new cars may decide to "increase his profit opportunity by installing an option . . . and that is a legitimate business practice."

Beyer said a dealer typically can get away with this practice "only if he has a hot product."

Consumers who don't want to buy dealer options obviously have the right to take their business elsewhere, and Rose advises them to do that.

"If you can't get the car without those features, go somewhere else," he said. "And if all franchises of that manufacturer are charging those prices, buy another kind of car."

To exercise that option, however, it helps to recognize the tricks of the auto trade.

For the past four months, for instance, Anton Motors has been equipping the majority of its new cars with an antitheft device called Auto Guard, which is operated from a switch in the glove compartment. If the switch is on, the unit will stall the engine within about 10 seconds of ignition. This foils a thief, if the thief doesn't know to switch off the Auto Guard before starting the car.

Any customer interested in a car that happens to be already equipped with Auto Guard would have to take the car with this $489 option, said General Sales Manager Kevin Hahne, because it is "too expensive to remove" the device.

If a customer doesn't want the Auto Guard option, they can buy another car that hasn't been equipped with the device, Hahne said.

Of course, he said, what the customer could get in the way of another car would depend upon what the dealership could locate or order. And for high-demand cars, such as the Toyotas sold by Anton Motors, that may be easier said than done.