Is diesel 1 worth the extra nickel per gallon when it is available?

not in my book, unless you are somewhere frozen. I believe diesel 1 is winter grade which will lower your fuel mileage. the way i think of it is if the manual tells you to use it during winter, must have some anti gelling additives and be known as winter mix. if it is, then less fuel mileage as most have reported.

Number 1 diesel fuel commonly referred to as kerosene

http://www.amghummer.com/Diesel/DieselFuel/about_diesel_fuel.htm

When I use to drive truck and deliver diesel to stations we would mix #2 fuel and kero in different ratios depending on winter temps. It would start off 80/20 (#2/kero) then 70/30, then 60/40 then reverse the process till it was warm enough to deliver straight #2 again. I would also add "Red Dye" to the trailer ( pulled a 12,000 gallon tanker http://www.jpnoonan.com/ ) sometimes if they needed off road fuel.

even the manual says to use Diesel 2 if you can..unless you live in a super cold climate.

#1 isn't some sort of premium diesel--it's designed only for cold weather use because it has less tendency to gel in extreme cold. This is because #1 is kerosene as stated before, and it has less lubricating properties.

I'm not sure where you're from, but I certainly wouldn't run #1! Run straight #2, especially this time of year. If it's really cold, then I'd suggest running an anti-gel additive such as Power Service, Primrose, Stanadyne, etc. I run an additive with every tank, so I feel comfortable using straight #2 down to about 0 to -10°F. However, most stations in Montana blend at an 80/20 mixture as a precaution in winter months anyway.

Bottom line, don't run #1 unless you absolutely have to!

step away from the #1 diesel!! ):h