(Bloomberg) -- Auto sales in the U.S. probably took a big step back in September, setting the stage for hefty incentive spending by carmakers struggling to clear old models from dealers’ inventory.

Deliveries of cars and light trucks may have slumped in September by about 12%, the average of six analysts’ estimates. Nissan Motor Co. is expected to lead declines among the major companies reporting Tuesday, as the Japanese carmaker continues to struggle in the post-Carlos Ghosn era.

The sales slowdown has the potential to put auto dealers already struggling with shrinking profit margins in an even more precarious position. With outgoing model-year vehicles clogging their lots, automakers had to pony up record incentive spending of more than $4,100 a vehicle in the third quarter, according to researchers at J.D. Power and LMC Automotive.

Detroit’s major auto manufacturers have stopped reporting monthly numbers, though General Motors Co. and Ford Motor Co. have scheduled the release of quarterly figures Wednesday.

Here are highlights from the carmakers that are reporting results for last month:

Toyota’s Tumble

Toyota Motor Corp. saw it sales plunge 16% in September, with both its namesake and Lexus luxury brands dropping by double-digit percentages. Deliveries fell for almost every model, including its best-selling RAV4 sports utility vehicle and Camry sedan.

While all carmakers are going to struggle with September having been a shorter sales month -- the Labor Day holiday weekend applied to August figures this year -- Toyota can’t entirely blame the calendar. Even on a daily selling rate basis, total sales were down 9.2%.

Palisade Powers Hyundai

Hyundai Motor Co.’s namesake brand may have weathered the month better than others in the industry, with sales slipping 8.8%.

The South Korean company started U.S. deliveries of the Palisade, a three-row flagship SUV, in June. While it’s quickly become one of the carmaker’s better-selling models, Hyundai was unable to measure up against the numbers it posted a year ago. It still expects to have gained market share for the quarter, Randy Parker, Hyundai’s U.S. vice president of sales, said in a statement.

--With assistance from Melinda Grenier.

To contact the reporters on this story: Chester Dawson in Southfield at cdawson54@bloomberg.net;Gabrielle Coppola in New York at gcoppola@bloomberg.net

To contact the editors responsible for this story: Craig Trudell at ctrudell1@bloomberg.net, Kevin Miller

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