Accidentally using low sulfur diesel fuel?

The technology has existed for several years to produce sulfur poisoning resistant DPFs and catalytic convertors. I suspect that GM is using this more advanced technology but I have been unable to confirm it through my contact.

As for the testing details, I can't post any more details for two reasons: 1. too much detail will make it obvious who I got the information from and I'm not about to compromise that person's confidence in sharing information with me, and
2. My contact will not tell me which part of the system contains the sulfur poisoning detector. This might mean it does not exist, and it might mean that the department doesn't want to identify it until they have a chance to see if it works in the field.

However, in order to identify the symptoms and extent of any damage caused by using LSD, tests HAVE already been done by GM. My contact is high enough up in the engineering pyramid to give me confidence that the results I was given are reliable. They have had trouble identifying any specific evidence of sulfur poisoning from their tests but I do not know how many thousand miles were simulated.

When, and if, I can get more information, I'll post it. In the meantime I'm still interested in finding someone with an LMM who has used LSD - at least several tankfuls. I've posted the question on several forums and have yet to find anyone who has been into Mexico with an LMM but it's hard to believe that nobody has yet done it.

Since I first posted my question I've done a huge amount of research on DOCs and DPFs and I've spoken with two US Govt sponsored researchers who have done work on DOCs and DPFS with respect to the effects of sulfur in fuel.

I now know what company manufactures most of the DPFs (Johnson Mathey), and I have access to several scientific papers documenting fuel sulfur effects on DPFs and DOCs.

Here is the bottom line summary of the data:

1.
The emissions system is designed to operate at a specific "break even" temperature for the exhaust gasses - this is a temperature at which the exhaust gasses, during average driving conditions, tend to facilitate continuous regeneration while driving, minimizing the need for fuel wasting active regeneration. Concentrations of sulfur in the fuel higher than 50ppm have the effect of RAISING the break even temperature - it jumps by about 30 degs when going from 50ppm to 350 ppm sulfur in the fuel. Obviously this leads to more frequent programmed regenerations under average driving conditions.

HOWEVER, towing a trailer, and/or driving at freeway speeds, naturally results in HIGHER exhaust gas temperatures, and the test results all support the presumption that using higher sulfur fuel while towing will have little or no effect on the system or emissions.

2.
When there is sulfur present in diesel fuel, SO3 is formed during combustion. Some of this SO3 combines in the DOC with water molecules in the exhaust stream to form H2SO4, sulfuric acid, which in turn creates a range of sulfates in reaction with soot particles. The end products are still particulate in nature, but much smaller and more dangerous to human health than the larger particles. This is the motivation for the EPA directive to reduce sulfur content.

There is also an impact on the efficiency of the DPF though - the smaller particulate sulfates created in the DOC tend to run right through the DPF, so although the soot is still burned off, the sulfates tend to escape and the total particulate emissions can actually INCREASE to levels higher than would have been the case with no DPF installed. The particles are no longer predominantly soot, but are mostly the much smaller and supposedly more dangerous sulfates, especially at lower exhaust gas temperatures.

At 3ppm sulfur the DPF achieves 95% reduction, at 30ppm it achieves 72% reduction, at 150ppm the reduction is almost at zero, and at 500ppm, typical of Mexican fuel, emissions actually increase above the baseline EXCEPT at higher exhaust gas temperatures. As mentioned above, the composition of the particulate matter in the emissions gradually changes to a higher and higher sulfate based material.

3.
None of the tests run in several scientific studies reported damage to any of the components of the system whether running 0% sulfur diesel (a new experimental fuel), various concentrations of sulfur up to 500 ppm, or biodiesel of various concentrations. However, the optimal blend at this time for the most effective reduction of emissions is 15ppm, which is what we are now getting at the pumps.

4.
Here are two links to comprehensive information about diesel particulate filters (DPFs) and Diesel Oxygen Catalysts (DOCs) and the effects of fuel sulfur on those components. These reports were generated during testing prior to legislation to introduce the components into vehicles beginning in 2007.

http://www.nrel.gov/vehiclesandfuels...pdfs/31600.pdf

contains the February 2002 Summary of Reports from the Diesel Emissions Control Sulfur Effects Project of the U.S. Government.

On page 8 appears the following quote “The performance of the DPFs when exposed to 400 hours of testing with higher sulfur levels did not degrade”.

However, higher exhaust gas temperatures are required for proper regeneration, which means that stop and start driving around town on higher sulfur diesel is not an ideal situation. Highway speeds and higher engine loading, such as when towing, do provide the necessary higher exhaust gas temperatures.

IMPORTANT: The report dispels the myth that there is any parallel between the catalytic convertors on cars which require unleaded gasoline and the DPFs on diesels. Lead in fuel irreversibly damages catalytic surfaces, but sulfur does NOT.

http://www.aecc.be/en/content/pdf/AE...00 final.pdf

is a July 2000 report from the Association for Emission Control by Catalyst which also describes sulfur tolerance tests run on DPFs.

On page 9 the report states that sulfur effects on the DPF are almost indistinguishable using fuels between 50ppm and 450ppm of sulfur unless the distances exceed 80,000kms (50,000 miles).

There is a lot of misinformation and speculation floating around about the effect that higher sulfur fuels, like that found in Mexico, could have on the DPFs and DOCs of the new diesel trucks, but none of the extensive testing done prior to introduction supports the notion that significant damage will occur.

However, it is a fact, also described in both reports, that particulate emissions actually increase if fuels with high sulfur content are used. This is the overwhelming reason why ulsd fuel has been specified for use with the new trucks – there was no point in introducing a DOC and DPF unless the emissions from sulfur could be reduced along with the soot.

Both researchers I have spoken with indicated that it is highly unlikely that any "damage" would be detectable in the DOC and DPF unless a vehicle used higher sulfur fuel for more than 25,000 miles. However, the emissions would exceed US Govt requirements while using the higher sulfur fuel.