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 20