Jet fuel, diesel fuel, and the lighter grades of fuel oil are collectively referred to as middle distillate fuels, from the fact that they are taken off the middle of a distillation column, below the light ends, such as gasoline and naphtha, and above the heavy ends and resids.

Kerosene

Today, most kerosene is refined further into jet fuel. Kerosene itself continues to have some market in domestic space heaters, lights and stoves for camping, and occasionally as a light grade of fuel for diesel engines, “power kerosene.”

Highly paraffinic Penn-grade oil makes excellent straight-run kerosene. Its original uses as fuel for domestic heating and lighting, require minimal sulfur content, because of odor, and low aromatics, to avoid smoke and soot formation. A typical boiling range for straight-run kerosene is 205–260 °C, indicating that the dominant components would be alkanes in the C12–C15 range, alkylcyclohexanes, and alkylbenzenes. Derivatives of decalin, naphthalene, or larger compounds could be in solution at low concentrations.

In addition to boiling range and sulfur content, other important properties of kerosene are its flash point and cloud point. Flash point gives some indication of safety in storage and handling. The flash points of various kerosenes vary widely, but all are above normal ambient temperatures, e.g. 45 °C. Kerosene is safer than gasoline to have in storage and to handle. Cloud point measures the temperature at which wax crystals begin to precipitate from solution; the name comes from the fact that the liquid takes on a cloudy appearance at this point. Operating at or below the cloud point can lead to problems with clogging of fuel lines or filters. For kerosene the cloud point is 15 °C or lower, so that in most cold-weather circumstances there would be little problem in handling kerosene.