There is a monster diff between summer and winter regarding MPG. When its 85f and sunny im getting 55-60 mpg depending on driving habits, and when the temp goes to 30f i get 45-50, and when the temp is in the sub zero or single digits i drop as low as 35 mpg. Still better than the 17 i was getting with my pacifica but a big diff overall for temp change. as far as mech aspect, it runs a little rougher in really cold weather but then so do i !!