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OAR Box 1132 

Prepped by Candice Davis 

Document Number: 

6) ll-C-3 

Docket Number: 

A-86-03 

Printed 4/18/2008 2:24:46 PM Sheet 6 of 122 
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A-U-c* 'jr-c-3 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Mr. John B. Curci o 0FF]CE0F 

Chief Executive officer AIR AND RADIATION 

Mack Trucks, inc . 

Executiv e Offices, Box M 

Allentown , PA 18105-5000 

Dear Mr. Curcio : 

Thank you for your letter describing your concerns with 

meeting the 1991 and 1994 diesel particulate standards and the 

effect of fuel sulfur content on such compliance. Briefly 

recapping our efforts in this area to date, in June of 1986 we 

distributed for comment a preliminary report on the effects of 

diesel fuel quality on emissions and performance. We have been 

analyzing the comments received on this report, and in addition 

have been preparing more detailed analyses of some of the key 

issues such as the effect of sulfur on engine wear, the 

conversion of sulfur dioxide to sulfate in the atmosphere and 

the effect of sulfur content on required engine control 

technology and cost. These analyses will be compiled into a 

study to be completed near the end of this year. A decision to 

proceed with a formal rulemaking aimed at regulating diesel 

fuel quality will be made upon completion of this study. 

One of the more difficult aspects of this study is our 

evaluation of the types of technologies that would be used to 

meet the 1991 and 1994 heavy-duty diesel particulate standards 

on current fuel versus a low-sulfur fuel and any resultant cost 

differential. Vie have requested detailed projections on this 

issue from all of the heavy-duty engine manufacturers in our 

meetings on trap development efforts. To date, a number of 

manufacturers have submitted general statements concerning the 

effect of low sulfur fuel on potential compliance. However, 

little detailed information supported by complete test data has 

been received. Such information is critical if EPA is to 

accurately quantify the effect of diesel fuel sulfur control on 

the heavy-duty diesel industry, and determine the industry's 

ability to meet the 1991 and 1994 standards with and without 

sulfur control. Thus, any additional information that Mack 

Trucks, inc. could supply on this issue would be very helpful. 
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Trap plugging is another area where the engine 

manufacturing industry could assist us in our study. 

Daimler-Benz has submitted evidence that about a third of the 

non-regeneratable particulate matter found on a trap was 

sulfate particulate. It appears that this non-regeneratable 

sulfate (e.g., a metallic sulfate derived from wear products or 

other metals found in oil additive packages) differs from that 

sulfate which passes through the trap. It seems possible that, 

even without sulfur in the fuel, these metals would combine 

with other anions and still plug the trap. Thus, any 

additional information Mack has on the composition of such 

particulate or on trap plugging with high and low sulfur fuel 

would be greatly appreciated. 

In summary, we are pushing ahead with our study, on the 

basis of our own analyses and the information we have received 

to date. Thank you again for providing your perspective on the 

importance of reducing sulfur levels in diesel fuel. I assure 

you your comments will receive careful consideration in our 

deliberation on this issue. 

Sincerely, 

J. Craig potter 

Assistant Administrator 

for Air and Radiation