Average gas prices in Fort Collins are up 5.1 cents per gallon over last week, averaging $3.55 on Sunday. Nationally, prices have gone up by an average of 1.3 cents per gallon to $3.8, according to gasoline price website FortCollinsGasPrices.com. Sunday’s prices were 2.2 cents per gallon higher than the same day a year ago and are 9.7 cents per gallon higher than a month ago. In the past 48 hours, the lowest price on regular gas that was available was $3.40 at Western Convenience at the corner of Mulberry and Riverside.  The highest price in Northern Colorado was $3.75 at stations in Fort Collins, Laporte and a few other locations. According to the Coloradoan, gas prices over the past month have increased by more than 14 cents and are also more than 14 cents higher than this time one year ago.