Diesel Fuel’s Quality Problem

Let us start with one simple fact, it is illegal to even sell gasoline without the minimum amount of detergent additives established by the EPA.  Specifically citing The Code, 40 CFR 80.161 – “Gasoline may not be sold or transferred to a party who sells or transfers gasoline to the ultimate consumer unless such gasoline contains detergent additives which have been certified according to the requirements of this section.”  While this minimum requirement is a necessary starting point most engine OEM’s today recommend going far beyond the EPA minimum requirements by encouraging that Top Tier gasoline’s be used in their engines.  For a list of all the leading retailers who have adopted Top Tier link HERE.

So one might wonder what would happen if you decided to run your car on raw gasoline and just ignored the detergent and performance requirements of modern engines? Likely nothing good.  Injectors would clog, emissions would increase, and you just might find yourself stuck on the roadside.  Despite that reality diesel fuel users both on the consumer side at home and in commercial fleets at work are doing that very thing.  They are dumping raw diesel fuel into a very advanced engine and many are learning the hard way this may not be a great idea.

Diesel has never had the best image.  From the black smoke bellowing out of that truck in front of you on your drive home to the scandalous Volkswagen emissions fraud case, diesel seems to work hard at looking bad.  But the other side of story is that diesel is a tenaciously competitive fuel.  It provides relatively cheap and dense BTU’s that are better at powering the engines that move heavy loads than anything else we’ve come up with.

Despite the many challenges diesel faces engine manufactures have recently made some amazing progress.  With the implementation of EPA Tier 4 Final in 2015 diesel engines of all classes now have nearly eliminated their smoke, soot, NOX, and SOX emissions.  The chart produced by John Deere below shows just how dramatic the reductions in pollutants have been since 1996.

So if this story is about diesel fuel quality why are we talking about emissions?  Well the progress on emissions has resulted in engines that put tremendous new demands on the diesel fuel.  The most obvious of these demands was the reduction of sulfur in 2006 for use in the 2007 model year engines.  What has been far less obvious is the unintended consequences of removing the sulfur from the fuel.  With sulfur removed diesel fuel can hold far less water in solution.  When that water drops out of solution in storage tanks the bacteria and algae that feed on the hydrocarbons while living in the water start having quite a feast.  In the process these organisms are creating a hideous mess inside diesel tanks of all shapes and sizes.

If we were still running diesel engines with large clearances and tolerances this wouldn’t be as much of an issue.  Now however, these 2010 and later diesel engines come with a very different set of technologies.  The High Pressure Common Rail (HPCR) engines of today operate at extremely high pressures up to 50,000 psi and injectors with clearances down to between 2-4 microns.  The example video below shows how many injector ports per cylinder the diesel must flow through.  Any one of these clogs with deposits or contaminants then fuel is wasted or the entire injector fails.

Emissions requirements have also resulted in engines with a daisy chain of emissions reduction equipment on the exhaust that includes a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) unit. Each of these components introduces new maintenance challenges and burdens on the engine and the fuel.  If injectors clog with deposits from dirty fuel, dirty tanks or unstable biodiesel the downstream impact on each emission control component can be severe.

So is this really a diesel quality problem or a diesel specification problem?  The short answer is both.  With sulfur out of the fuel diesel tanks simply require a much more stringent maintenance and cleanliness regime than they have had in the past.  Keep the water out and the bugs and algae won’t grow.  Sounds simple, but that leads us back to the diesel specification itself, or the ASTM D-975 specification for diesel fuels in the US.  More specifically for the vast majority of fleets we are talking about, “1.1.4 Grade No. 2-D S15—A general purpose, middle distillate fuel for use in diesel engine applications requiring a fuel with 15 ppm sulfur (maximum).”

To spare you reading the 27 page specification let us summarize the primary areas contributing to our biggest quality concerns:

• Can contain up to 5% biodiesel and still be labeled ULSD #2.
• Can contain up to 500 parts per million of water and sediment.
• No minimum requirement for detergent or dispersant.

Now nothing wrong with biodiesel of course most progressive fuel suppliers are integrating biodiesel into their diesel fuels and in several states you simply do not have a choice.  The challenge with using increasing amounts of biodiesel is that at the temperature and pressures of modern diesel engines there are likely to be deposits formed in the engine if no additive chemistry is employed to provide detergentcy.

Water in the fuel may sound like an obvious issue but perhaps at just 500 parts per million it is really not something to worry much about.  Well to illustrate just how much water that is consider this if each truck load of 7000 gallons of diesel fuel came in just below the specification that would mean that there are 3.5 gallons of water in every truck load of fuel.  You just thought the water cooler guy was the only one delivering water to your business, seems he may have some competition. 

So if you are dumping nearly a 5 gallon pail of water in your diesel tank every time you get a load of diesel and that low sulfur diesel no longer holds that water in suspension let’s guess what we find in our tanks at the end of a year.  I am not even going to talk about the sediment part of the specification let’s just assume running dirt through an engine with 2-4 micro clearances is on the face of it a really bad idea.

As a big fan of diesel in general I hope we can clean this up, but like any problem getting to a solution starts with some recognition that the problem is real.  On that note I am starting to see a few suppliers run at this problem instead of away from it.  They are offering advanced additive treatment programs, tank cleaning and maintenance solutions, and first and foremost talking with their customers openly about the challenges with diesel fuel quality.  Those marketers and suppliers that get in front of this to protect their customers are going to take share and win business.