summer MPG

[zeno]

Have an '18 Silverado. In winter the city MPG runs apx 18MPG.
Then with hot weather it goes up to 22MPG. Why ? Is it summer VS winter
fuel ? Never travel in winter but summer HWY MPG goes as high as 30MPG
at times & averages high 20's . Thats not a snap shot but over a 100 mile + ride. Did the math & it figures when I refill making the read out spot on.
Comments ?

73 Zeno
LFOD !