A popular Chicago-area pizza chain is offering a new discount — and it’s all tied to gas prices. Giordano’s Pizza on Friday began what it called a “Save a Gallon” promotion, offering discounts equal to the average price of a gallon of gas off any pizza order. “The discount will refresh weekly based on AAA gas prices, giving customers ongoing savings through the summer season,” Giordano’s said in its announcement. The promotion applies only to loyalty members via the chain’s app. It began Friday with gas prices averaging $5.43, the chain said.