By Paul Nazzaro, Advanced Fuel Solutions, Inc.
It won’t be long before municipal fleets are out hauling salt spreaders to de-ice the roads. The general principle is simple: salt lowers the freezing point of water; the more salt you add, the lower the freezing point; the colder the temperature, the more salt (or salt solution) it takes. Those behind the wheel of the vehicle often assume that the same rule applies to the low temperature operability of their fuel—the colder the temperature, the more cold flow additive it takes to lower the cold weather operability of the fuel and eradicate fuel gelling. This misconception commonly leads to a phenomenon known as reversion, wherein the performance gains achieved by the proper dose of the additive are reversed due to an overdosing of the fuel.
While it’s true, in a sense, that salt is to water as cold flow additives are to fuel, the two chemical interactions are actually very different. While salt inhibits crystallization of water molecules, cold flow additives modify the size and shape of the wax crystals that precipitate in diesel fuel under cold conditions, enabling the fuel to flow freely through engine components without plugging filters.
It’s important to recognize that cold flow additives are themselves waxy materials, meaning that they actually add more wax to the system. The dosage must therefore be carefully calibrated in order to achieve the optimum response. Raising the dosage above the recommended treat rate will offer little or no additional benefit, and, in extreme cases, will cause a reversion of low temperature properties that can leave the fuel even worse off than its pre-treated state.
Fuel can generally be over-treated with any kind of additive, in any type of application. High levels of certain lubricity improvers can react with contaminants (sodium, calcium, etc.) to form materials that cause filter plugging. Going too high with a corrosion inhibitor in the presence of the same contaminants can cause internal injector deposits. In short, every category of additive has a treat rate that is too high. Overdosing—particularly in combination with common fuel contaminants—can result in a loss of engine performance and fuel efficiency, and, worse, may damage expensive engine components.
Overdosing can happen for any number of reasons, at any point in the supply chain—at the refinery, due to (or in response to) an ‘upset’; at the terminal, due to a control valve malfunction at the rack; or at the pump, where a driver adds a bottled product assuming that more is better, or accidentally treats fuel that has already been treated upstream.
For the municipal fleet manager preparing for winter, it is important to work with reputable fuel wholesalers and additive suppliers, to know your recommended additive treat rates, and to monitor your fuel quality to ensure that proper additive levels are used.
For more information on fuel additives, monitoring, or premium treatment solutions, contact Paul Nazzaro at 978-258-8360 x301 or firstname.lastname@example.org.