More auto numbers will come in later in the day, but the initial reports show Mixed Sales Results in March.

The top two U.S. auto makers reported mixed results for March amid growing concerns about the industry’s inventory levels and reliance on discounts.

General Motors Co.reported a 1.6% sales increase in March to 256,224 units compared with the same month a year ago. The Detroit, Mich., auto maker said its retail sales were up 5% in March to 203,113 units.

Ford Motor Co. reported a 7.2% sales decline in March compared with the same month a year ago. The Dearborn, Mich., auto maker pulled back on fleet sales and experienced a substantial decline in passenger-car sales.

Top Japanese auto makers, meanwhile, reported mixed U.S. sales results in March, with Honda Motor Co. HMC -0.73% posting a 0.7% decline and Nissan Motor Co.reporting a 3.2% increase.

Ford said fleet sales dropped 17% in March, due in large part to the timing of customer orders. Retail sales for the No. 2 U.S. auto maker fell 1.5%.

Industry watchers are keeping a close eye on inventory levels, which are tracking near historic highs and forcing auto makers to ladle out generous discounts. A glut of used cars flooding the market is also pressuring new-car prices.

The average incentive is expected to reach 10.4% of the sticker price, exceeding the 10% level in March for the first time since 2009 when the country was navigating the financial collapse, the research firm said.

Also troubling to analysts is the number of days a vehicle sits on a dealer lot before being sold. That number is expected to reach 70 days in March, the highest level for any month since July 2009, according to J.D. Power.

I expect this report will take a couple of ticks off GDP estimates, but other reports are out today that also factor into GDPNow and Nowcast GDP estimates.

Auto sales account for approximately 20% of retail sales. A sustained slowdown, which I expect, will be a drag on GDP for some time.

Mike “Mish” Shedlock