Diesel Fuel's Quality Problem
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
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:
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.