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2007 Diesel Engine Emissions


With the move to new emissions technology in 2007 there are a host of questions regarding diesel engines, which fuel to use, etc. We'll try to answer some of these questions in the following section.

1) What is low sulfur diesel fuel?

Actually, the fuel dispensed in pumps prior to 2007 is Low Sulfur Fuel LSD). The 2007 spec engines will require Ultra Low Sulfur Diesel Fuel (ULSD). LSD contains a maximum sulfur content of 500 PPM (parts per million) while the newer ULSD can contain no more than 15 PPM sulfur content.

2) Why the change?

The EPA has created new regulations to reduce nitrous oxide (NOx) emissions levels. In order to do this, the sulfur content of the fuel needs to be reduced. New high efficiency catalytic devices will be used on the 2007 spec engines to burn these particulates up. However, in order to operate these devices it is mandatory that the ULSD diesel fuel is used or else the devices will fail.

3) When do the new engines show up?

The EPA regulations enforce that any engine built after January 1st, 2007 must meet the 2007 emission specs. Note that this is as of the date of engine manufacture. If the engine that is built in December of 2006 is placed into a chassis in the beginning of 2007 and then a motorhome is first installed on that chassis is April of 2007, it is exempt from the 2007 emission specifications because it is in fact a 2006 engine. However, there are certain rules that prohibit engine manufacturers from building engines in advance and stockpiling them. Considering the typical inventory levels of both the coach builder and the chassis builder plus assembly times and advance planning it is expected that the new engines probably will first begin to show in a finished product around May of 2007, which outs them into the 2008 model year. This will vary between the various manufacturers and coach models according to how good they guessed at demand.

4) When does the new fuel show up?

The EPA has requirements as to the timing of the fuel transition. California has their own schedule, which is stepped up. The EPA requires the refineries to be making ULSD by June 1, 2006. It must be delivered to the terminals September 1, 2006 and available at retail pumps by October 15, 2006. Note that off-road and marine fuel has until June 1, 2007. California has stepped up retail delivery of ULSD fuel to September 1, 2006 and includes off-road fuel in that group as well. Canada has also chosen to adopt the EPA's October 15, 2006 implementation date.

5) How do I know what fuel I am putting into my tank?

The EPA requires that labels be placed on every diesel fuel pump. If it is an ULSD pump, the label will state "Ultra Low Sulfur Diesel Fuel". If it is an LSD pump it will be labeled "Low Sulfur Diesel Fuel" and a warning will be posted stating that this fuel will damage emissions equipment of 2007 or newer diesel engines. These labels are not required to be posted on California pumps because California has mandated that only ULSD fuel will be available, both on-road and off-road.

6) What fuel can my engine use?

If you have a 2007 spec engine you must use the ULSD fuel with it's low 15 PPM sulfur content. If you use any fuel with greater than 15 PPM sulfur you will damage the engine's diesel particulate filter (DPF) and affect it's drivability. If you have an earlier engine you can run either LSD fuel with a 500 PPM sulfur content or the ULSD 15 PPM fuel.

7) Will the new ULSD fuel hurt my pre-2007 engine?

By reducing the sulfur content in the fuel, the aromatics were also reduced. These aromatics contribute to the fuel's lubricity. Without lubricity your fuel injection pump and injectors would score and seize up. To counteract this refiners have found no ways to add lubricity agents to the fuel. Reducing the aromatics also reduces the elastomericity of the fuel and in some cases gaskets and seals within the fuel system may dry out and begin to leak. The Clean Diesel Fuel Alliance anticipates that the vast majority of engines will not need any changes to their fuel system when switching over to ULSD fuel. However, in a few cases, most notably older high mileage engines, fuel leaks may develop and these gaskets will need to be serviced.

8) Will the ULSD fuel burn as well as the existing LSD fuel?

The processing required to reduce the sulfur also reduces aromatics which increases the cetane number and decreases the density of the fuel. The BTU per gallon of fuel will also decrease but the reduction in energy content is around 1% so effects on fuel economy should be minimal.

9) Can I use the same engine oil as before?

The new ULSD engines require API CJ-4 oils. Previously most oils were API CI-4 spec. The CJ-4 oils have reduced ash and zinc content. Because some oil gets consumed during operation, it will pass through the Diesel Particulate Filter (DPF) on it's way out the exhaust. The DPF, which is a high tech catalytic converter, cannot have "stuff" fouling it up or else it will fail. For these reason the new AP-I CJ-4 oils are designed with reduced deposits that could foul the DPF. Think of it as ULSD oil for your ULSD engine. These new oils can be used in pre-2007 engines as well. They have been designed with greater high temperature tolerances and increased anti-wear additives so the new oils will be great for any engine. The important thing is not to use the older API CI-4 oils in the new engines. The oil manufacturers do not recommend mixing CJ-4 and CI-4 oil together. While the oil is compatible, the additive packages are not. Chevron has introduced their Chevron Delo 400 LE API CJ-4 motor oil in June of 2006 and Shell has upgraded their Shell Rotella T with an API CJ-4 version, also available June 2006. However, the previous API CI-4 oils are also still available so be sure to read the label before you buy.


Submitted by Mark Quasius - 10/2/06

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