NEW YORK - An article yesterday at FoxBusiness.com explained the basics behind credit and debit card use as it relates to gasoline purchases, relying substantially on insights from NACS.

"I don't think the average consumer has any idea what goes on behind the scenes when they swipe a card," said Jeff Lenard, vice president of communications for NACS, whose expertise was relied on heavily for the article. "The credit and debit card system is incredibly complex."

Among the complications the article cited:

1. The station could impose transaction fee limits that prevent customers from filling their tank (especially common as gas prices increase).
2. Computer "blocks" and "holds" could trigger bounced transactions. ("That's the one that really causes consumers a lot of angst," Lenard said.)

Lenard also explained that as consumers use credit and debit cards to purchase gasoline, fuel marketers "are probably losing money."

The article addressed issues that consumers should assess when purchasing gasoline, citing available balance and interest rate as primary considerations.

The piece then explained transaction limits, whereby a station imposes a limit on the size of the purchase, a practice designed to protect the station from losses. "Since for pay at the pump there is no signature required, there could be an increased risk of fraud," said Matthew Towson, a spokesperson for Discover.

A typical limit is $50, which doesn??t present much of an issue during times when gas prices are low. But as prices approach $4 a gallon, customers with large vehicles can frequently exceed $50 or even $75 limits, preventing a fill-up.

"Two things happen [in such a scenario] and they're both bad," Lenard said. "The customer comes into the store and goes from being just annoyed about the price to being outraged. 'I'm trying to fill up. Why did you do this to me?'"

Lenard said the customer could initiate a second transaction, which is an inconvenience for the customers as well as costly for the retailer (as it incurs a second swipe fee).

Blocks or holds present additional obstacles, as card companies and banks block or hold a higher amount than the customer might need (up to $100 at a gas station) for up to three days, a practice implemented because station owners and other service industry merchants do not know at the outset exactly how much the customer will spend on the transaction. These blocks or holds are especially significant for consumers who are nearing the limit of their available balances.

For debit card users who carry a low balance in their linked bank account, this can be problematic, too. As such, the article recommends frequenting a store that requires PIN numbers, which usually eliminate a hold.

The article deferred to NACS for the last word on gasoline purchases, an act it said is fraught with behind-the-scene complexities rather than any conspiratorial design, a practice that marketers undertake with a focus on convenience.