mpg

It all depends on the blend. Usually it comes out to 10-15% less.

 

I always noticed a drop in power and mpg when the blended fuel came out, on older trucks, anyway.

 

4% of the drop is due to winter fuel blends having less BTU. The rest is due to weather and temperature. Cold air is denser than warm air and takes a lot more energy to push through.

 

Untreated diesel fuel begins to jell at 17.5 degrees.
If you are idling (overnight) and the temp drops to let's say 10* you ain't gonna jell up... Because your return line is heating your fuel in the tanks.
If you are driving, it is just as unlikely to happen.
If the truck is sitting for a day or two, with untreated diesel and the temp drops . .. You got problems .
Most larger truck stops treat their diesel.
Regular diesel is #2
Extreme weather diesel is #1
Yes, you will get slightly lower mpg with treated diesel. Barely enough to notice. #1 you will notice significant drop
Best thing to use, (this is 30years experience) is the white bottle of diesel power service . It prevents jelling and increases cetane rating which equates to better mpg