We’re now almost 10 years out from the initial implementation of the ULSD rule for diesel fuel. Initial predictions of doom and gloom from the industry have not been fulfilled as feared, but have been replaced by other consequences. A little knowledge for you, the user, can go a long way towards knowing what these changes really do mean for you and your vehicles, fleet and business.
Everyone is well familiar with “ULSD” fuel (ultra-low sulfur diesel). The old high-sulfur diesel from the 1980s was replaced by low-sulfur diesel fuel in the 1990s, with 90 percent of the sulfur removed. Ultra-low sulfur diesel fuel replaced that, starting in 2006, with a further 97 percent of the sulfur removed. So the diesel fuel we’re using now has less than one-half of one percent of the sulfur your parents' and grandparents’ diesel fuel had.
This has been wonderful for the environment, but industry insiders predicted certain “ill consequences” that would follow. They were mainly concerned with the lubricity of the diesel fuel, predicting that sulfur removal would leave the marketplace with a diesel fuel that couldn’t properly lubricate injectors and fuel pumps. Wear problems were sure to follow. Other industry insiders up north predicted winter flow issues with the ULSD fuel, citing that the refinery processes used to take out the sulfur would substantially raise the temperatures at which this new diesel fuel gelled in the winter.
How right were they?
A decade in, how right were they? Partially. The lubricity problem was a legitimate concern, but the marketplace responded with new fuel treatments that would give the ULSD fuel back the lubricity it lost. Not only that, but the wide-scale introduction of low levels of biodiesel into the diesel fuel supply have effectively solved these lubricity problems because of its tremendously high lubricity rating.
Winter cold flow issues haven’t been so easy to solve, but diesel users in the frosty north have made it their winter routine to use cold flow improver treatments. So no real change there, other than the fact that the current ULSD fuels still need a little more treatment on the cold flow side than the high sulfur fuels of the past.
Greater concerns
Concerns about lubricity and cold weather handling have been replaced, for ULSD users, by greater concerns over storage stability and resistance to microbial growth.
Stored diesel users used to be able to get several years (or more) of viable life from the diesel in their storage tanks. The transition to ULSD has completely changed that. Typical storage life has now run less than a year before legitimate fears over the fuel’s viability in the storage tank can arise.
The most pressing issue concerned ULSD storage life started as an afterthought. While fuel professionals know that water buildup in storage tanks could lead to development of “microbe problems,” it was assumed that simply keeping that water under control was all that was needed to keep microbes at bay.
Because sulfur functioned as a natural “biocide,” removing virtually all of it from diesel fuel gave us fuel with virtually nothing in it to keep microbes from growing and thriving. Now, it’s no longer enough to keep on top of water problems. Even a small amount of water in storage tanks is enough to results in microbial growth. And every storage tank has some amount of water in it.
Microbe problems are a serious matter because they destroy fuel quality, plug filters and damage expensive storage tank equipment with their corrosive byproducts. And they can spread everywhere the fuel is used. A fleet that has an infected fueling tank will eventually see microbe-induced problems in all the fuel systems, machines and vehicles that use that fuel.
Microbes not withstanding, today’s ULSD fuels have shorter shelf lives because of a greater level of inherent instability. They have more heavily cracked and hydro-treated than the fuels of yesteryear – these refer to the processes used at the refinery level to squeeze out the required yields of ULSD from crude that the market demands. So even if a company or fleet’s fuel storage tanks can be kept microbe-free, the ULSD fuel in those tanks has a shorter storage life because they start with more of the “precursors of instability” – unstable fuel molecules that initiate and participate in the chain reactions that lead of fuel darkening and stratification.
What It Means For You
No longer can someone leave fuel in storage tanks, checking on it once a year (if that). There are solutions to extend and protect fuel storage life, and fuel storage professionals are highly recommended to consider them. Stored fuel is too expensive of an investment to leave its quality to chance.
