(FORTUNE Magazine) – Save for the big automakers, Warren Young may be the nation's leading car salesman. But you won't see him on TV hosting tacky ad spots with balloons and marching music. Young, 63, a former mechanic, is CEO of Manheim Auctions, the nation's largest used-auto auction company. While new-vehicle sales dropped 4.8% nationally last year, Young's volume accelerated some 8%. Most of the growth has been in leased and rental cars, popular among consumers because they sell at big discounts to new cars. Manheim, owned by Atlanta's Cox Enterprises, just merged with a rival jointly owned by GE Capital and Ford Motor Credit. The new enterprise will sell about two million cars, worth some $12 billion, in 1991, generating an estimated $500 million in fees for Manheim. The alliance with Ford, which owns part of Hertz, may bring Manheim even more of the used-rentals business. It will also drive away with some of the traffic from GE, which leases about 450,000 fleet vehicles to companies like FMC and Union Pacific.