Then she rented a Hertz car with the NeverLost global-positioning system, a satellite-driven navigation unit that gives detailed directions to destinations. Within months, the Northridge, Calif., resident became a GPS devotee, paying a total of about $4,100 for two units -- one each for her 40-foot Monaco Dynasty motor home and her Jeep Grand Cherokee.

"We used to spend so much time getting lost," said Mrs. Hume, a workshop coordinator who travels the country with her husband 10 months out of the year. "Now it's like we have an angel giving us directions with every turn."

Another renter-turned-buyer. The rental-car industry has become a powerful marketing tool for new automotive technologies and new cars themselves (though in some cases car makers still use rental agencies to dispose of slow-selling vehicles). And the marketing has proven equally advantageous for rental operators, who often negotiate for exclusive rights to offer new cars and products first.

Experts say rental cars are a perfect test-drive for potential buyers. They say that after driving a rental car for a few days, customers can end up buying a car and accessories they wouldn't ordinarily consider.

"By putting cars in a rental fleet, you're developing a potential customer base," said Neil Abrams, president of Abrams Consulting Group, a Purchase, N.Y., consulting firm for the rental-car industry. This year, Mitsubishi Motors Corp. released its 2003 Outlander and General Motors Corp. supplied its 2003 GMC Envoy and Chevrolet TrailBlazer simultaneously to Enterprise Rent-a-Car Co. and dealerships. The goal: get more of the SUVs in front of potential buyers faster. Normally, it takes a few months for new models to hit rental-car fleets.

DUAL APPEAL - Source: car makers, rental agencies Some vehicles launched in rental fleets and dealerships simultaneously: * Ford Motor -- 2002 Explorer * Mitsubishi Motors -- 2003 Outlander * General Motors -- 2003 GMC Envoy and 2003 Chevrolet TrailBlazer

Enterprise, which gets 95% of its business from neighborhoods, rather than airports, is particularly attractive to car makers because many of its customers rent cars as insurance replacements. These customers drive the cars during their normal routines and thus are more likely to influence their peers' perceptions of a particular model.

Ford Motor Co., which owns Hertz, used the agency last year to push its redesigned 2002 Explorer replacing a model under fire for safety concerns. Aiming to boost its tarnished image, Ford seeded the Hertz fleet as it began shipping the new vehicle to dealers.

"Our view is rental fleets are a great opportunity for passive marketing," said Ford spokesman Mark Schirmer. "This is a way for people to get into a Ford product without having to be in a dealership and having to hear a pitch from a salesman."

Honda Motor Co. also has been pushing its Insight and Civic Hybrid cars, which run on gasoline and electricity, into rental fleets. That can help sales even when it if the renter isn't buying, Honda says.

"First, we view [rental companies] as customers ... and as a secondary benefit, they're raising awareness to the consumers about these cars," said Stephen Ellis, manager of Honda's alternative-fuel vehicles.

Honda has sold hundreds of its alternative-fuel vehicles to Budget EV Rental Cars, a partnership between closely held EV Rental Cars and Budget Group Inc. and the nation's only company that exclusively rents "green" cars. The Los Angeles company also rents two cars powered by natural gas, the Honda Civic GX and a special version of Ford's Crown Victoria, as well as the low-emission Nissan Sentra and GM's electric EV1. The cars cost the rental-car company more to maintain and service, but rent at a premium.

Bill Orr never considered owning a Civic Hybrid or Toyota Prius, both of which get double the highway miles per gallon of his Honda Odyssey minivan, until he rented several on business trips. Now the manager at the California Environmental Protection Agency said he's thinking about buying one. The Sacramento resident also plans to suggest an electric hybrid to a friend who's looking for a new car.

For Thales Navigation Corp., a closely held Santa Clara, Calif., company that makes the NeverLost system, being in the Hertz fleet has been the prime driver of sales of units that average $1,800 each.

A recent J.D. Power & Associates study of 6,000 car buyers who bought navigation systems found almost one-third had prior exposure to them, with more than half saying they got that experience in a rental car. Thales said it sells about 7,000 units a year -- with no advertising -- because about 80% of its customers try its systems in rental cars.

Thales won exclusive renting rights with Hertz, which has Thales systems installed in 50,000 domestic vehicles. A rental car with the system costs as much as an extra $8 a day. "We are selling units despite no marketing activity," said Ajay Prasad, Thales's vice president of vehicle marketing.