Martin's and Giant have partnered with suppliers to offer points to customers for specific purchases. Wachter, for example, bought five bottles of Pantene shampoo and conditioner to earn 200 extra points — giving her enough to save 40 cents per gallon for her trip to the Delaware shore.
Wachter said she doesn't believe in "buying a discount." But she uses Pantene regularly, so she took the promotion as an excuse to stock up.
"It did prompt me to read the weekly circulars a little more closely," she said. "In this case this is something I would spend money on anyway."
Wachter, who says she drives about 2,000 miles a month, takes several approaches to saving on gas.
She just switched to a Hyundai Elantra because it does not require premium fuel. She typically gases up at Costco, which sells fuel and other products to members at a discount. When she has accumulated 200 Giant points — enough for a 20-cent-per-gallon break — she heads for Shell.
"I tend to hoard the gas points until it really makes a difference," she said.
Wachter said she probably wouldn't participate in the program if the Giant in Elkridge and the Shell station were not convenient to her home.
That's the reaction some Safeway customers have to the chain's Reward Points program, which enables discounts at five Safeway gas stations in the Baltimore area, in Bel Air, Catonsville, Edgewater, Perry Hall and Pasadena.
"If you have a Safeway fuel station near where you live, you think this is wonderful," said Ten Eyck, the spokesman. "It's not effective to earn your loyalty unless there's a Safeway fuel station somewhere near your home."
For some, the program seems to work.
"I definitely have become more of a Safeway shopper," said Roxanne Umphery of Catonsville, who also uses her Safeway Club Card to earn an additional discount of three cents per gallon.
Crystal Brown's husband uses the points she earns at Giant to help fuel his SUV. "It makes a big difference," the Owings Mills woman said.
Ganem, of Loyola University, said consumers should consider not only price, but the total cost of making a purchase.
Ganem, the author of The Two-Headed Quarter: How To See Through Deceptive Numbers and Save Money on Everything You Buy, compared buying products to earn a discount to driving across town to chase cheaper gas or to redeem a coupon. Consumers would use up gas and time — both limited resources.
Ganem said the gas discount programs are intended to be complicated to make price comparison difficult.
"My belief is a lot of the confusion is to make it impossible for you to make rational decisions in the marketplace," Ganem said.
Stores must spend some money to put these programs in place, he pointed out, and those costs drive up the prices of all the products sold.
"Obviously they're getting more economic benefit than the cost of running these programs," he said. "Since it's costing them money to confuse you, they must be getting a lot more money back than they're spending, or they wouldn't do it."
"It would be better for consumers if there were none of these programs and if you simply paid the market price for what it was when you bought the item," he said.
Miller, the Giant spokesman, took exception to this, saying he thought Giant customers saved not only through gas rewards but also through additional corporate branded items and other sales.