Frequent Questions

Due to the known reproducibility problems in testing at a 15 ppm level, would EPA consider letting downstream entities "average" the sulfur level tests within a range - say no more than 20 ppm maximum and 15 ppm average - to avoid supply disruptions?

No. As stated in the preamble to the final rule, the sulfur sensitivity of emission controls that will be used on model year 2007 and later motor vehicles requires that the sulfur content of highway diesel fuel dispensed into 2007 and later heavy-duty vehicles not exceed 15 ppm. Consequently, under the rule, the 15 ppm sulfur standard is a cap that must be met on a per-gallon basis. However, during the transition period, highway diesel fuel of up to 22 ppm may be sold as ULSD (beginning June 1, 2006 through October 14, 2006).

Also, to account for test variability downstream of the refinery gate or import facility, we allow for a downstream test adjustment of negative 3 ppm through October 14, 2008 (this adjustment will revert back to 2 ppm on October 15, 2008). The purpose of taking testing variability into account in compliance determinations for fuel sampled downstream of the refinery or import facility is merely to ensure that fuel actually meeting the 15 ppm cap is not rejected and treated as noncompliant due to concerns about testing variability. It is not expected to result in any increase in the actual sulfur content of highway diesel fuel above 15 ppm at any point in the distribution system. Note, however, that the rule does not limit the ability of the fuel distribution industry to set a commercial pipeline sulfur content specification. We acknowledge that pipelines may elect to set sulfur specifications.

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