Gas prices are starting to go back down as the price of crude oil and demand falls. Triple-A Arizona says the average price of gas in the state is $5.20 a gallon, which is down 13-cents from last week. Diesel gas is also coming down some. The average price of diesel is $5.85 a gallon, which is down over five-cents a gallon from last week. The Energy Information Administration says over the last two weeks demand for gas has decreased and U.S. supply has increased by around two-and-a-half million barrels. With the combination of lower crude oil prices, gas prices have started to decline. In Flagstaff, the average price for regular gas is down four cents from last week to $5.10 a gallon. Diesel is down over nine-cents a gallon to $5.96 on average. In Prescott, the average price of gas is down nearly two-cents a gallon to five dollars even. Diesel is down over ten-cents to $5.80 a gallon.