Gas prices have levelled off in Arizona. Triple-A Arizona says the average price of gas this week is unchanged from a week ago, sitting at $3.99 a gallon. Diesel fuel is down about two-cents a gallon from last week to $4.96 a gallon. Triple-A spokesman John Treanor says the reason for the levelling off has to do with refineries. He says, “this is when oil refineries schedule routine maintenance and inspection.” Treanor adds, “it happens every three-to-five years for oil refineries, and when it happens it takes those refineries off the system so they can go through very important maintenance and inspections.” The process drops supply enough to have an effect on prices. In Flagstaff, the average price of gas fell nearly two cents a gallon to $4.10 this week, while diesel is down just over two-cents a gallon to $5.02. In Prescott, the price of gas this week is four-dollars a gallon on average, which is down over two-cents a gallon from last week. Diesel fuel is down around two-cents a gallon this week to $5.03.