Diesel Fuel Q and A

 

Question?
What is diesel fuel?
 
Answer
The term diesel fuel can reference several products including burner fuel, heating fuel, X-grade, D-grade, fuel oil and others. Most commonly it refers to a distillate with properties that will allow it to be burned in compression combustion engines and/or home heating systems. Diesel fuel is a complex mixture of hydrocarbon molecules derived from petroleum crude. The variation of these molecules is significant, depending on the crude source and refining technique. 

Question? 
How long can I store diesel fuel?  

Answer
Tank location and storage temperatures have a great impact on a fuel's storage life.  As diesel fuel is stored, it slowly reacts with oxygen in the air to form gums and varnishes.  As temperature increases the reaction also increases.  The addition of contaminants such as water or rust can accelerate the process. Generally, a fuel should not be stored longer than six months.  If long term storage is required, then the tank should be underground or inside to reduce temperture extremes, and must have proper ventilation caps.  If storage exceeds one year testing is recommended

Question? 
What is algae and how do I get rid of it? 

Answer 
In fuel labs, the term algae implies bacterial or fungal growth.  There are several forms, but they all live in the water and feed on the fuel.  They generally show up as a black, slimy substance that plugs the filters.  They most often occur in farm storage tanks that are seldom used, as algae likes dormant, warm conditions. 
Water is the key ingredient.  If a tank is regularly drained of condensation then no problems will occur.  If water does accumulate and growth occurs, then the tank should be cleaned and treated with a biocide. 

Question? 
How is low sulfur diesel fuel made and is it really better for my equipment? 

Answer 
The most common refining process for making low sulfur fuel is hydrotreating.  Crude feed stock is heated to a very high temperature, and high pressure, in the presence of hydrogen.  The molecules formed are very stable and free of contamination.  Fuel made with this feed stock contains fewer sulfur and aromatic compounds.  Lower sulfur limits the formation of acids that attack metal surfaces.  Fewer aromatics mean a fuel less likely to react with oxygen to form gums or varnishes. 

Question? 
Can I use gasoline in my diesel fuel in the winter to improve starting performance? 

Answer 
Only if the equipment manufacturer recommends it.  Even a small amount of gasoline (0.5%) can alter the physical properties of diesel fuel and make it much more hazardous to handle.  While diesel engines are capable of short-term operation with a wide range of fuels, it is not generally in the long-term interest of the unit. 

Question? 
I had my storage tank filled at the end of winter, will the carry over of winter blended fuel cause problems in the summer-time? 

Answer 
No operational problems should be expected.  Winter cold flow improvers or the addition of No. 1 fuel will not cause summer problems.  Large additions of No. 1 could decrease the BTU content of a fuel causing slightly less power, but even straight No. 1 has less than 5% fewer BTU's than No. 2, so the difference is generally unnoticeable. 

Question? 
What is the most common cause of problems involving the fuel pump and fuel injectors in diesel equipment? 

Answer 
Contamination.  Dirt, water, and other airborne materials cause far more problems than anything else.  Most of these problems are correctable.  Good house cleaning practices involving storage tanks and frequent maintenance (filter replacement) can prevent most of the pump and injector wear that results in premature repairs. 

Question?
What does cetane do and how important is it? 

Answer 
Cetane is a measurement of the ignition delay of a fuel.  A higher cetane number means a shorter delay and better ignition quality.  A compression engine without the benefit of a spark must have fuel that is self-igniting.  That self ignition is most important at start-up and provides quicker ignition and less pollution.  Most equipment manufacturers recommend a minimum cetane of 40.  Premium fuels generally have cetane values over 45.  Cetane is calculated two ways.  "Cetane number" is the result of an acutal engine test while "cetane index" is a value calculated from the fuel's physical properties. 

Question?  
Why does my diesel engine smoke? 

Answer 
Diesel engines smoke is caused by incomplete combustion.  White smoke is caused by tiny droplets of unburned fuel, resulting from an engine that is misfiring at low temperatures.  This smoke should disappear as your engine warms up.  Black smoke can be from faulty injectors, insufficient air, or overloading/ over fueling of the engine.  The blue or gray smoke is the result of burning lubricating oil and is an indication the engine is in poor mechanical condition. 

Question? 
What can I do after my fuel has already gelled? 

Answer 
Generally speaking, the gelled fuel must be warmed above its cloud point temperature to redissolve the wax.  This can be done by putting the equipment into a warm area or installing tank heaters.  The replacement of gelled fuel with a more suitable winter blend is highly recommended.  It is important to remember that if the fuel is not above the cloud point and you add No. 1 fuel or chemical flow improvers, it will be ineffective.  Since ice crystals are frozen water this can also cause unwanted symptoms in gelled fuel.  Be sure to maintain a dry fuel system, especially in the winter season. 

Question? 
Does fuel color affect performance? 

Answer 
No.  There is no relationship between the natural color of diesel fuel and such desirable performance qualities as heat content or cetane.  Diesel fuel color can change with the crude source, refinery methods and the use of dyes.  However, if the fuel color darkens during storage, this could indicate oxidation and/ or contamination from dirt, water or other sources which can lead to operation problems.