pump up the tires if you can handle the hard ride.for every 10F drop in temps you automatically lose 1psi due to expansion/contraction formula not air loss.
use 5w30 motor oil which can give you 1-3mpg.sometimes mid-grade or premium gas will give you a few more mpg if you dont have a lead foot.low temp do influence mpg becauce gas doesnt vaporize as well as in warm moist air.dont panic.it will warm up and your mpg will slowly improve.