MasterCard, Visa and Discover are setting secret limits on how much you can purchase at the pump with a credit or debit card and being caught by surprise at the card shuts off beofre the tank is full.

"Using my Visa card, I commonly hit a limit and I would be standing there scratching my head," Shawn Bloomfield, who pumps premium gas into his SUV, said from his home in Allentown, Pa. "I would always assume it is the gas station setting a limit on how much gas I could purchase. It felt like a ration scenario."

As the price of gasoline continues to rise, rules to prevent credit card fraud at the nation's pumps are confusing consumers who just want a full tank of gas.

Caps on transaction amounts _ or the total dollar amount of gas a customer can pump into their car are a pain in the butt for some drivers of gas-guzzling vehicles.

"When I go to the gas station I now have to use two credit cards just for one tank of gas," said Paul Brisgone of Oxford, Pa. "Kind of defeats the convenience of pay-at-the-pump."

Brisgone, a field operations manager for a telecommunications company, said he alternates between three different credit cards,two Visa and one MasterCard, when filling up the 32-gallon tank in his Ford F-150 pickup.

Credit card companies say the policies, which aren't new, but with the sky rocketing of fuel prices more people are running up against the fuel purchase limits. The limits are designed to ensure that merchants and consumers are protected from fraudulent transactions that could occur at a gas pump and hurt the Visa, MasterCard, American Express or Discover card networks.

Credit card companies have established a protective layer by setting caps on how much gas a consumer can pump at any one given time. For MasterCard customers, it's $75. Visa and Discover users have a $50 pay-at-the-pump limit. Transaction limits vary for corporate card holders and American Express users.

The good news is that there are typically no limits if a customer goes inside and pays with their credit card at the counter.