For those who can't access Travelers link, here is the text:
The life expectancy of stored diesel fuel is limited. Depending on the amount of contaminates, sooner or later stored diesel fuel will deteriorate. Of the many contributing factors, there are four main factors responsible for the deterioration of marine diesel fuels.
These factors include:
oxidation
microorganism growth
corrosion
sedimentation
Reviewing briefly the first three factors; oxygen reacts with the hydrocarbon molecules in the fuel. Oxidation causes discoloration, formation of particulates, water and gum. Microorganism growth, primarily bacteria and fungi, gather at the fuel water interface in the storage tank. They consume diesel fuel and produce acids and water as byproducts. Corrosion is caused by microbial growth, water and voltage potential across storage tank walls. Corrosion may deteriorate tank walls and releases metals back into the stored fuel. This action will accelerate the oxidative reaction.
--------------------------------------------------------------------------------
Sedimentation is a consequence of the fact that marine fuels are not pure hydrocarbons; they contain inorganic matter such as grit, clay and sand. These substances, to some extent, occur in the crude oil and remain in the residual fuel after refining. In addition, other non-oil soluble material may enter the fuel during storage and distribution. These sediments can generally be removed from the fuel by settlement, centrifuging and filtration, depending in their density and particle size. Tests methods used to identify these materials, do not assist in the evaluation of the fuel regarding long term precipitation of asphaltenes.
Several studies have confirmed the effects of the factors discussed above. University of Idaho scientists have conducted tests to determine the timeline and percentage of degradation of stored diesel fuel #2. The results from this testing shows that petroleum diesel fuel #2 degraded 26% after 28 days of storage. Studies conducted by Frankenfeld et.al. under accelerated storage conditions also proved that sediments are formed. The formation of these sediments are increased in the presence of water and dissolved oxygen. [references: "Fuel Facts" National Biodiesel Board, Jefferson City, MO; Frankenfeld, J.W. "General Features of Sediment Formation in Model Fuel System," Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 608-614].
Before proceeding we should discuss substantial myths about diesel fuel, and in particular, the use of the term Algae with regard to diesel contamination. Virtually every diesel fuel additive makes reference to Algae on it's label. To further perpetuate this myth, AlgaeX incorporates the term in it's name. I received an email recently from someone promoting the AlgaeX products. While the author did not sufficiently identify himself, I found the contents of the correspondence to confirm much of what has been written above. I have paraphrased in the paragraph below, excerpts from this email for the historical perspective as to how diesel sludge came to be called Algae.
The shelf life of diesel fuel is approximately 100 days from the day it is refined, then it begins to break down and form sedimentation. The breakdown process causes diesel fuel to cluster up and fall out of solution, dropping to the bottom of the tank. This forms diesel sludge. The fuel begins to turn dark in color, smell bad and in most cases cause engines to smoke. The engines smoke because some of these clusters (in the early stages) are sufficiently small micron size to pass through traditional filtration and into the combustion chamber. As these cluster increase in size only the outer edges get burned, the rest goes out the exhaust as unburned fuel. Further increases in sedimentation cluster size begins to reduce the flow of fuel by clogging filters. The filters only address the symptom and not the cause. Then there is this word Algae. There is absolutely no algae in diesel fuel; you may have fungus and microbial contamination but no Algae. This is a misnomer for the problem that someone tagged on it many, many years ago.
