For several years winter was a mix of diesel, fuel, or kerosene. Now there are lots of gas additives that provide you fuel in less price.
Be sure the fuel in your bulk tanks is treated. If using a mobile fleet fueling service, ensure that they are treating during the cold weather months. Make sure your fuel is treated to be protected down to the coldest geographic areas where your trucks run. You can choose the fuel repair option through the internet.
With the new biofuels/biodiesel blends, always ask your supplier if they are using a biofuels blend and if they are treating that fuel. Biodiesel is more difficult to treat for trouble-free winter use than low sulfur diesel or ultra-low sulfur diesel.
An accepted method of fuel testing is for cloud point or CP. The newer method is to test for cold filter plugging point or CFPP. The CFPP is the lowest temperature at which fuel will still flow through a specific filter.
Ask your supplier if they are performing either of these tests on the fuel you are purchasing and what the cold-weather performance of their fuel.
In most states, with idling restrictions, the days of leaving a truck idle all night to ensure it makes its run in the morning are gone. Most have engine block heaters. These should be plugged in when the engine is still hot. They are designed to maintain the engine's heat, not heat a cold engine.