"Gas prices are dropping everywhere in South Carolina," said Sarah Davis, AAA Carolinas public relations manager. "We're seeing reports that gasoline supplies are healthy right now."

Just a week ago, gas prices soared to $2.79 per gallon. Yet, prices have dropped as much as about 25 cents since then, according to SouthCarolinaGasPrices.com, a Web site that follows local gas prices.

But don't look for the downward spiral to continue. An increase is just around the corner, Davis said.

"Memorial Day really kicks off the summer driving season," she said. "We're expecting demand to increase for the summer. At that time, we may see prices shift back up."

Davis couldn't speculate how high prices would rise as the holiday nears.

For now, the national average price is $2.90, Davis said. The average price for gas in South Carolina is $2.73. In Rock Hill, the average gas price is $2.65.

On Monday evening, two Anderson Road gas stations offered gas at $2.54 per gallon. Eight motorists, including Pat Warren, gased their cars at Energy USA as four more waited for their turn at the pumps.

"I saw the price and stopped," said Warren, a Charlotte man who works in Rock Hill. "I always fill up down here. It's usually 10 cents cheaper on the average."

One reason for lower gas prices in South Carolina is the gas tax, Davis said. The gas tax in North Carolina is 29.9 cents per gallon, while the gas tax in South Carolina is 16 cents, she said.

Down the road from Energy USA, Patricia Holland pumped gas at Lesslie Food Mart No. II.

"I'm pretty happy about it," Holland, 31, said about the gas price. "Everybody else is like $2.64. This is probably one of the two cheapest that I've seen so far."

Katrina Boozer, a Fort Mill resident, waited in her Dodge Neon at Lesslie Food Mart as her 12-year-old son, James, pumped gas.

"In Fort Mill, gas is $2.79 a gallon," said Boozer, 34, who works in Rock Hill. "I come down here a lot to get gas. It's a lot cheaper."

Davis of AAA Carolinas said two factors -- transportation costs and competition -- influence gas price.

"If people make a concerted effort to find the cheapest gas in their area, then retailers will respond with lower prices," Davis said.

And, she said, it costs to deliver fuel.

"The closer you are to the source, i.e. the pipeline, the fewer transportation costs there are, and the cheaper gas will be typically," Davis said.