The mpg on my Latitude did improve after time although it was not anywhere as low as you are getting. The odometer turned 84k today and over the lifespan of the Renegade the average mpg is 27.8 mpg. On a trip to Florida last April I averaged about 31mpg roundtrip, the best I have done. Do you have the 2.4L or the 1.3L? Five minute trips will not help, especially if you live in a cold climate.