Costly customer rebates and other incentives also drained G.M. cash, averaging about $1,000 a car, according to many analysts.

The Buick division of the General Motors Corporation extended customer rebates for most 1990 and 1991 Buick models through April 7.

In ordering Nynex to pay customer rebates for poor service, the commission cited the company's widespread service problems from September 1995 to September 1996.

His agency, he said, has closed 89 transactions and returned $900,000 in customer rebates.

For years, auto makers have tried to control prices by offering customer rebates and dealer incentives, with mixed results.

The $462.5 million bond sale is intended only to pay for a one-time customer rebate and rate reduction during the next five years, not to finance the buyout.

The highly visible and popular customer rebates were introduced in the mid-1980's to stimulate sales of slow-selling models and reduce large inventories.

For example, G.M.'s Oldsmobile division switched its rebates to dealers only in November 1989, but sales declined and customer rebates were soon restored.

"There is so much confusion in the marketplace about customer rebates," said Ross Roberts, general manager of Ford's Lincoln-Mercury division.

Tests in the Northwest Ford decided to switch to dealer incentives from customer rebates after testing the program at dealerships in the Pacific Northwest.