Anyone else seen this big a drop in gas mileage?

[ripcord]

I think I figured out another factor in the gas mileage drop, my battery was bad so the start\stop system wasn't functioning properly. Steering feels different too.

A bad battery can affect how it runs quite a bit.

 

[Donald]

Some are happy their car even starts when the temp is below 0F.

 

[carviewsonic]

Even on a long highway trip (6 hrs) that I have done dozens of times over decades (to visit family), mpg drops 20 - 25% in -30 degree weather compared to milder weather. Higher air density and rolling resistance, winter fuel blend, and transmissions not warming up completely are some of the causes.

 

[Donald]

Even on a long highway trip (6 hrs) that I have done dozens of times over decades (to visit family), mpg drops 20 - 25% in -30 degree weather compared to milder weather. Higher air density and rolling resistance, winter fuel blend, and transmissions not warming up completely are some of the causes.

Cold air in the air intake is better than warm or hot air for maximum power from engine combustion. That's why vehicles with turbos have intercoolers.

But that may not be a big enough gain to offset the other cold temp issues.