General Motors Co. increased incentives on its full-size pickups in the first 10 days of July after sales declined following a high-profile June advertising campaign that questioned the durability of rival Ford Motor Co.’s aluminum-bodied trucks.

According to J.D. Power, discounts on the Chevrolet Silverado were up 76 percent from June to an average of $7,962 and 147 percent on the GMC Sierra to $9,457. During the same period, Ford incentives averaged $4,457 for it’s F-150 series trucks, while Fiat Chrysler Automobiles offered discounts of $6,172 on its Ram pickups.

For the month of June, year-over-year sales of the Silverado declined 3.7 percent and dropped 7.8 percent for the Sierra, while Ford saw deliveries of its F-Series jump 29 percent.

GM responded to the discount numbers by maintaining that its incentives were up early in the month as a result of a 20 percent off sticker price promotion.

“Fully half of the full-size pickups sold to retail customers during the first 10 days of July were a Chevrolet Silverado or a GMC Sierra,” Cain said, noting that GM expects its average discounts to be on par or below FCA and Ford for the month.

As part of its Chevy Summer Sell Down event, GM is continuing to offer 20 percent off of some models, including $10,042 cash back on the four-wheel drive version of the 2016 Silverado 1500 Crew Cab LT All Star.