(Garden City, UT) — The average price for a gallon of gas in Utah is now four-dollars and 20-cents. Triple-A says the most expensive average price can be found in Rich County where gas is four-dollars and 47-cents. The least expensive average price is four-14 in Duchesne County. Gas is going for an average of four-19 in Salt Lake County. Nationally, the average price for a gallon of gas is now over four-dollars.