Regular gas prices are approaching the five-dollar a gallon mark across Arizona. Triple-A Arizona says the average price of regular gas is $4.92 a gallon, which is over six-cents higher than last week. Diesel fuel is $5.49 a gallon, which is nearly unchanged from a week ago. Triple-A Arizona spokesman Aldo Vazquez says prices are higher simply because of supply and demand. Vazquez says, “we are dealing with a tired supply and increased demand that have pushed pump prices higher and this supply and demand dynamic, and volatile crude prices, will keep upward pressure on pump prices for the foreseeable future.” In Flagstaff, the average price of regular gas is $4.80 a gallon, which is nearly four-cents higher than last week. Diesel is $5.59 a gallon, which is actually three-cents lower on average than a week ago. In Prescott, the average price of gas is $4.65 a gallon, which is a cent higher than last week. Diesel is $5.47 a gallon which is over two-cents lower than last week.