The Nature Of Diesel

According to a study performed by the University of Idaho in 1994, it is estimated that Low Sulfur Diesel degrades as much as 26% in the first 28 days.


Like all fuels, diesel has a natural shelf life. diesel is considered an organic fuel and like all organics it decays with age. Diesel can be reliably stored for 12 months at an ambient temperature of 20°C (65°f) and 6 to 12 months at 30°C (86°f).

Molecules in the fuel lengthen and bond over time creating asphaltines (diesel sludge). Diesel sludge can clog in-line filters and damage critical engine components. As a hygroscopic fuel (one which attracts moisture from the atmosphere) diesel often contains freestanding and emulsified water. Water can enter your critical reserves from vents on storage tanks, poorly designed storage systems, the distribution chain and interval engine testing required by local and national legislation.

Emulsified water is water which is absorbed by the fuel. This molecular bond can hold with such tenacity that traditional fuel water separators fail to remove 40% to 100% of entrained water.

With the desulphurization of diesel over the last two decades and the introduction of bio-blended fuels operators need to be aware that fuel integrity can be compromised in less than 12 months and legacy fuel management programs may not be enough to protect emergency engines.

Just as hydrodesulphurization produced unforeseen side effects in diesel fuel lubricity, additives and biodiesel create a less obvious, but equally dangerous unintended outcome: failure of existing fuel-water separators. In short, ULSD blends containing sufficient lubricity additives to pass wear requirements, and ULSD blends containing biodiesel, create conditions where commercial fuel-water separators fail to remove 40-100% of fuel-entrained water. The insidious aspect of this side effect Is that there is no way for an operator to know it is happening. - - Christine Stanfel - PhD - Ahlstrom Filtration - LLC