O'ahu drivers, who watched gasoline prices top $3 a gallon for regular at some stations this week, should prepare for another 13-cent increase next week.

On Monday, the state raised the cap on wholesale gas prices by 14 cents, and Advertiser calculations show the price could climb another 13 cents next Monday. The state Public Utilities Commission will release the official numbers today.

At French Wrench Shell on Queen Street prices went up 9 cents a gallon yesterday to $2.969 for regular in response to a comparable increase in the station's wholesale gasoline prices, said Mike Verner, the station's manager.

The state's price cap law, which took effect in September, sets the maximum wholesalers can charge each week based on an average of Mainland wholesale prices. Retailers are free to charge whatever they want but have generally been sticking close to the changes in the wholesale cap.

State lawmakers are considering suspending or lowering the gas cap.

Next week's wholesale price for regular on O'ahu could rise nearly 13 cents a gallon to $2.44. When taxes of about 53 cents a gallon and a retail markup are added, the price for regular in Honolulu could surpass $3.10 a gallon.

Prices at several stations around O'ahu have already exceeded $3 a gallon for regular for the first time since November, according to Honolulugasprices .com.

Other stations were charging as little as $2.75 yesterday, the Web site reported.

"That's what the gas cap does," said Shannon Wood, a Kailua resident who said she bought regular gasoline yesterday for $2.85 a gallon after passing a station selling it for $3.01.

"You can save money over time," Wood said. "What irks people is you're forced to be thrifty and shop for the lowest price to take advantage of the gas cap."

This week's jump in the price cap may have been partially offset by an 8-cent-a-gallon tax break linked to a requirement as of April 2 that Hawai'i gasoline contain 10 percent ethanol.

Reach Sean Hao at shao@honoluluadvertiser.com.