DETROIT -- General Motors notified its dealers this morning that it will be extending its 0 percent financing sale through Monday, July 7.

"As you'll hear later in our sales call today, it turned out to be a successful program. And when we've run it before, it's been a success as well," said Pete Ternes, a GM spokesman.

The sale conditions remain the same -- 0 percent financing for 72 months on most GM vehicles. The so-called 72-hour sale ran from June 24 through June 30.

"I think it's a good move on GM's part to start July out strong," said Lynn Thompson, owner of Thompson Sales Co. in Springfield, Mo. Thompson sells Buick, Pontiac, GMC, Cadillac and Saab vehicles.

Thompson said his floor traffic improved dramatically during the sale, and he sold some full-sized pickups and SUVs. But some customers need more time to make a purchase decision.

"It's hard to pull the trigger real quickly in just a week's time," Thompson said.

Another Detroit area dealer said he was losing sales because of the short period of the original sale.

"We might be dead for the next few weeks, so we've got to keep the momentum going," said the dealer, who asked to not be identified.

GM's Ternes said the automaker will heavily advertise and promote the sale, especially over the July 4 weekend.

Dealers see better traffic

GM dealers say the "72-Hour Sale" did spark more floor traffic and gave sales a shot in the arm. Still, many dealers finished the month below their June 2007 sales.

At Thompson Sales Co. in Springfield, Mo., June sales came in 16.5 percent below the same period last year. "I can't tell you how dismal the first two weeks of June were," says owner Lynn Thompson. "It was just wow…bad."

Thompson says he hoped to sell 50 new cars during the 72-hour sale and he sold 46.

"We sold some big SUVs," Thompson says. His store sells Buick, Pontiac, GMC, Cadillac and Saab. "When you think about what you're saving on finance charges, that buys you an awful lot of gasoline. It basically buys them two and a half years worth of gasoline."

At Jones Dealerships in Lancaster, Pa., the sale helped the dealership finish June up from a year earlier, says owner Steve Jones.

"It was a roaring success," Jones says. "The week before we had not sold a single GM vehicle. That's how slow it was. When they announced the sale last week, we sold 18. Our traffic was up by at least 50 percent compared to the beginning of the month."

Jones sold 44 total new GM vehicles in June, 18 of them came in that last week during the 72-hour sale. He sold 36 vehicles in June last year. "I would have never have guessed that we'd be up," Jones says. He says the main increase was in car sales.

In Flint, Mich., Randy Lauria saw floor traffic in three stores increase by 30 percent in the last few days of the month due to the 72-hour sale. Lauria sold 33 vehicles at Patsy Lou Chevrolet, 19 Buicks and 21 GMCs at Patsy Lou Buick-GMC and six vehicles at Patsy Lou Pontiac, he said. Lauria is general manager of the stores.

Those sales comprise 30 percent of his total monthly June sales, he said. Still the Buick-GMC store finished the month with sales down by 28 percent, Pontiac broke even and the sales at the Chevrolet store finished up by 10 percent, he said.

Still Lauria is angry with how GM handled the sale, especially with the last minute extension to July 7.

"GM said this would absolutely not be extended," Lauria says. "We were here until 11:30 last night delivering cars and telling customers it was the absolute last day. So our credibility is out the window and we're the representative of GM and for GM to mislead us makes me mad."

Use car deals announced

Meanwhile, GM said it plans to offer a nationwide rate incentive program on certain GM certified used vehicles.

The new rate incentive offer, effective through Sept. 30, provides well-qualified GM vehicle buyers with 2.9 percent APR financing for terms up to 48 months, or 3.9 percent APR financing for terms up to 60 months on 2003-2008 models of Chevrolet Impala and Malibu vehicles.

Well-qualified customers also can receive 4.9 percent APR financing for terms up to 60 months on 2003-2008 models of Chevrolet Trailblazer, Tahoe and Suburban; GMC Envoy, Yukon and Yukon XL; Pontiac G6; and Buick Lacrosse vehicles at participating GM dealers.

Thomson Financial contributed to this report