#1 or Winter Blended Diesel fuel

Cenex stations in Iowa and South Dakota sell RoadMaster, which is a 50/50 blend. Usually runs 20-30 cents a gallon higher. When its really cold, adding Howes is cheap protection. Cheaper than a road call for a gelled truck.

Another silly stupid thing to prevent problems when it gets really cold is to let your truck coolant warm up to at least 150° before you pull out for the day.

 

And in a pinch...wild Turkey dries brakes out!

 

And if your truck has heated tank fuel returns, you can hold a very high idle to ensure your tanks are toasty. The coolant temperature needs to be close to 180 as you ever can get it or higher.

 

Very true @kemosabi49