General Motors Co. says demand for fullsize light-duty pickup trucks is “a little bit ahead of objective” through August, leading senior executives to suggest the market is ripe for the auto maker’s all-new heavy-duty offerings.

Compared with like-2009, last month’s sales of the light-duty Chevrolet Silverado and platform-mate GMC Sierra jumped 8.8% and 3.9%, respectively, according to Ward’s data, which is adjusted for the number of selling days. There were 25 last month, compared with prior-year’s 26.

Through August, Silverado deliveries were outpacing like-2009’s total by 11.9%, while Sierra sales were ahead by 9.6%.

What is the source of pickup demand? “We’re seeing a lot of small commercial buyers,” says Don Johnson, vice president-U.S. sales operations.

While acknowledging the pace of economic recovery has slowed, GM believes a double-dip recession is a low-risk possibility, barring “unforeseen shock,” Johnson adds during a conference call with journalists and industry analysts.

The performance of the Silverado and Sierra helped limit a decline in GM’s overall light-truck deliveries to 4.5%. Meanwhile, a 39.6% plunge in GM’s car sales contributed to a 21.5% slump.

It was the first time since December the auto maker failed to record a year-over-year monthly increase, according to Ward’s. But August 2009 represented a challenging comparison because of the sales spike induced by last year’s government-backed “Cash for Clunkers” buyer-incentive program, and because GM has trimmed four brands from its lineup since then.

However, with the exception of Chevrolet, the remaining marques were well in positive territory when compared with their respective performances in August 2009. Buick’s numbers bookended its stablemates with the largest boost (126.1% in car sales) and the smallest (15.1% in light truck).

Chevy was below par in both car and light truck deliveries, posting declines of 29.4% and 8.8%, respectively.

Through August, total GM sales rose 6.3%, compared with like-2009.

Johnson and Chevrolet sales chief Alan Batey say the surge in pickup deliveries is welcome because GM’s redesigned-for-’11 HD models now are funneling onto dealer lots.

Heavy-duty models accounted for about 30% of the auto maker’s total August pickup sales.

Regarding the light-duty Silverado, Batey says: “We’re in a good place right now. We’re getting a lot of traffic.”

Johnson is unfazed by a proposed change to new-vehicle window stickers that would feature a large letter-grade as a measure of fuel economy instead of numerical performance ratings. Utility tops the shopping list for pickup buyers, he says, so a big “C-” on a Silverado’s sticker would have little impact.

According to sample grades provided this week by the Environmental Protection Agency and Department of Transportation, only hybrid versions of GM pickups would merit more than a C+, based on the nation’s ’10 model-year fleet.

Hybrid Silverado deliveries more than doubled in August compared with like-2009, but they totaled just 328 units – less than 1% of the 33,756 sales of conventionally powered Silverados.

Hybrid Sierra sales totaled 51, down 13.1% from prior-year.

Total light-vehicle sales to fleet customers accounted for 28.1% of GM’s August business, up from prior-month’s 25.1%. But Johnson predicts a decline by year’s end.

The ’11 Chevrolet Cruze small car “is going to have a significant impact on that,” Batey says, referring to this month’s market launch of GM’s all-new replacement for its C-segment Chevrolet Cobalt.

emayne@wardsauto.com