Preserve is an antioxidant, metal deactivator and color stabilizer. The active chemistry helps to neutralize acid build-up and delay the onset of metal reactions (yellow and ferrous) that can catalyze the fuel to degrade and form polymerized material (sludge, asphaltenes). Preserve also contains a water separator (demulsifier) and strong cleaning chemicals that help to inhibit growth.
Though the diesel fuel will eventually still degrade Preserve helps to delay that. Preserve should be added to new fuel, it will not fix fuel that has already begun to fail.
Preserve is compatible with on and off road diesel, bio-diesel and bio-diesel blends.