SEEKING CLARIFICATIONS
I enjoyed reading “Modern Diesel Fuel” by Christian Koop (Apparatus: the Shops, October 2013) and benefited from the information. However there are a few areas that I believe are not accurate.
The first point is that a direct link between diesel exhaust and cancer has not been established either medically or legally.
The second point is that diesel particulate filters (DPFs) would not have become mandatory in 2007. The Environmental Protection Agency (EPA) establishes emissions limits but does not require any specific technology to meet them. However, many engines at this time did adopt DPFs. The terminology is important.
The third point is that high levels of sulfur in the fuel would also damage the catalysts that are now used in a selective catalytic reduction (SCR) after treatment system. And related to point two, in some cases, engines now operate at a higher combustion temperature to minimize the production of particulates, so they would not now have or need a DPF. The greater amounts of NOx then produced are treated by the SCR system.
The fourth point is that cetane values in Europe went up from 38 to 40 in 2000-not in the United States-and typically European diesel fuel has been at a higher cetane value, now somewhere in the high 40s. United States cetane values are in the low 40s, and the engines are designed around this value, as it is the fuel commonly available. It is unclear why the engine manufacturers would now want a value around 50.
The fifth point is regarding the quality of diesel fuel and what evidence the author has that it varies greatly from location to location and why it is not as tightly regulated as gasoline, since the same entities would tend to regulate the two products.
It seems that the article builds up to a justification for the 128-page document for further information on diesel fuel-and perhaps a product to sell. The link, however, does not work.
If the readers supply their diesel-powered products with fresh fuel and ensure that it is clean-stress very clean-they should not run into any problems.
John Fischer
Engine Consultant
Palatine, Illinois
Christian Koop responds: Before I begin, I must state that this article was intended to give the reader unfamiliar with diesel fuel a brief history and general background to present day so those individuals would have a better understanding of this fuel type and the changes it has undergone.
Point 1: All the information I have read over the years indicates that there is a link between cancer and diesel exhaust. The American Cancer Society states that there is a link between lung cancer and exposure to heavy diesel exhaust on its Web site. Laboratory testing has indicated that lab rats exposed to diesel exhaust have developed lung cancer. Additionally, there are several other agencies including the State of California that state there is a link between diesel exhaust and lung cancer. Yes, the modern diesel engines with the DPF and SCR technology emit very clean exhaust in comparison to older units; however, there are many preemission units still in service. Benzene, which I do not mention in the article, is a component of diesel and is a known carcinogen. I understand this may be a gray area, depending on your perspective. However, I try to err on the side of health and safety. That was my main concern when I mentioned cancer-to make the readers aware of this possibility.
Point 2: Technically, Fischer is correct in that the EPA does not mandate the technology to be used. However, most manufacturers did address the new EPA limits by developing and using DPF technology. There was one manufacturer that did not, “bought emission credits” from the EPA, and held off installing the technology until later. By and large, the standards the EPA placed into effect beginning in 2007 were addressed by most manufacturers beginning in model year 2007 with the introduction of the DPF technology. I did not feel it was necessary to go into this level of explanation in this article. The purpose of mentioning the EPA and DPF technology is to give the average reader a better understanding of why diesel fuel has been transformed to meet the changes required by the new standards and new technology.
Point 3: I understand and agree with the points Fischer is bringing up. However, given the limitations I have in article size, I did not feel it important to delve into this area. I did mention in the fifth paragraph that upcoming changes in the EPA standards and resulting technologies would require reformulation of diesel to reduce the sulfur content.
Point 4: This should have read “Europe.” The United States still requires cetane to be a minimum of 40, and this requirement dates back to 1993. I have had diesel cetane levels tested many times over the years and have seen many inconsistencies. The fuel we are currently receiving has cetane levels that are well above the mid 40s.
Point 5: I have personally seen inconsistencies with the quality of diesel fuel over the years and have colleagues that experienced the same issues. That is why I begin the article by stating that how diesel fuel is stored and transported can affect quality. There is considerable documentation available on this subject, and the diesel fuel you’re receiving may have been handled many times during transportation and distribution. The more it’s handled, the more chances it has to get contaminated. Yes, gasoline and diesel are regulated by the same agencies. However, for some reason, diesel is not enforced in the same manner as gasoline. For example, I do not recall seeing a gasoline pump that was not properly marked with the decal required by law to indicate the octane level. However, I have seen many diesel pumps that had no decals indicating the cetane levels.
There is much information available about this subject. Cetane levels do vary, and if yours fall below the standard, it can affect engine performance and fuel economy. I mentioned the 128-page document from Certified Labs for those readers who may want more information on this subject, as it gives information on how testing is conducted. I am not trying to sell any products, and I do not know why the link did not work. However, I have visited the site and read the document.
For today’s high-pressure diesel fuel injection systems, it is critical that fuel be very clean. Fuel injection pressures in some engines are reaching as high as 30,000 pounds per square inch, and to withstand those working pressures the tolerances in the fuel injectors must be very tight. If water or fine particles get past the fuel filters, they can damage these very expensive components in short order. As Fischer points out, for the most part if the fuel is very clean-as he stresses-the end user should not run into any problems. That is why I believe it is very important to know the quality of the fuel you are putting in your emergency response vehicle’s fuel tank. I feel you need to be informed, and to be sure, you need to get the fuel tested by a reputable certified lab. Just keep in mind that cetane ratings that fall below standards can contribute to harder starting, ignition delay, power loss, and decreased fuel economy. Using a cetane improver additive, if needed, can improve ignition and reduce white smoke during cold weather startups. If it is not up to standard, you can waste dollars not only in fuel but also in repairs.
