State lawmakers want to make it illegal for gasoline wholesalers to increase their gas prices to retailers more than once in 24 hours. Retailers are already prohibited from raising prices they charge motorists more than once in the same day. Legislation proposed by Democratic Sens. Nicholas Sacco and Joseph Vitale would levy fines of up to $5,000 for a wholesaler's first offense, and up to $10,000 for subsequent ones. Republicans announced a package of measures to allow retailers to sell gas below their posted prices if the customer has a prepaid gas card; lower their posted prices during ``unpredictable price fluctuations;'' prohibit gas from being sold at excessive markups, and increase penalties for those who steal gas by driving away without paying for it. Another GOP measure would require refineries and suppliers that operate in the state to keep gasoline, diesel fuel and heating oil on reserve. Democrats also are proposing to increase of fines for service stations that raise prices more than once in 24 hours. The penalty for a first offense would increase from $50 to up to $1,500, and up to $3,000 for subsequent violations.