Hawai'i motorists could see a 5-cent or 6-cent increase in gasoline prices next week because of an expected hike in the state's wholesale gas cap.

The state Public Utilities Commission today will announce the cap that takes effect Monday. Wholesale gasoline prices have risen on the Mainland in the past week because of speculation about rising oil demand due to cold weather, as well as concern about petroleum stockpiles.

Honolulu prices for a gallon of regular could rise to about $2.50 at the least expensive stations. Pump prices aren't regulated by the law that went into effect on Sept. 1 but have generally followed changes in the wholesale cap.

The cap is based on wholesale prices over five days in New York, on the Gulf Coast and in Los Angeles. The Advertiser estimates the cap by using market data from Bloomberg News while the state uses figures supplied by the Oil Price Information Service.

The data sources can result in a few cents difference with what the state announces.