Average retail gasoline prices in Modesto have fallen 1.6 cents per gallon in the past week, averaging $2.60/gallon Sunday, according to GasBuddy’s daily survey of 201 gas outlets in Modesto. This compares with the national average that has increased 1.5 cents per gallon in the last week to $2.22/gallon, according to gasoline price website GasBuddy.com. Including the change in gas prices in Modesto during the past week, prices Sunday were 3.3 cents per gallon lower than the same day one year ago and are 10.9 cents per gallon higher than a month ago.