My mileage dropped nearly 2 mpg Dec 1st. No changes to my truck. I seem to recall reading here this is normal during winter months. First time I've seen it, but first time I've had a big fuel economy readout staring me in the face.

 

I usually see 1-2 mpg drop in the winter with the winter blend fuel, nothing to worry about.

 

The difference in winter fuel is less than .5 mpg. Cold temps make a much bigger difference.

 

In your location, vendors have been pumping winter blend fuel since circa mid-September. If you're just now noticing a MPG drop, it's related to lower average ambient temps, not the fuel blend.

 

Actually the mas airflow during winter detect a increase of air density and the computer put more fuel to respect air/fuel ration 14/1. If you heat the incoming air the computer will decrease the amount of fuel.

 

Agree with mike. Its a combo. Im in the frigid north so things like rear fluid are a slushi when i get going. Takes more fuel to push through that

 

I went from 20.5 to 19.7 for the past 2 weeks. Cooler weather.

 

I've gone up from 17 to 19.5 . But that may just because I stop flooring it this week. Trucks getting old almost 1000 miles Lol

 

Yes, between the colder, denser air and winter blend gas, your mpg will drop. My wife has had 3 of the Prius, they even dropped also. Usually 2-3 mpg, get back up in the spring.

 

Yeah I see a drop when it gets into the 40s. In the 30s it really tanks.