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Control of Emissions From New and In-Use Highway Vehicles and Engines: Approval of New Scheduled Maintenance for Diesel Particulate Filters in Certain Applications

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Environmental Protection Agency (EPA).




This notice announces that EPA has established a minimum interval of 80,000 miles (or 2400 hours) for the scheduled maintenance (cleaning) of diesel particulate filters used in some space-constrained truck applications. This minimum interval applies for model years 2007-2009. Diesel particulate filter cleaning is considered critical emission-related maintenance.

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David Dickinson, Compliance and Innovative Strategies Division, U.S. Environmental Protection Agency, Ariel Rios Building (6405J), 1200 Pennsylvania Avenue, NW., Washington, DC 20460. Telephone: (202) 343-9256. E-mail address:

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The Agency adopted new emission standards for heavy-duty diesel engines (HDDEs) in 2001 (66 FR 5002; January 18, 2001). These standards will result in the introduction of new highly-effective Start Printed Page 11412control technologies, beginning with a phase-in over the 2007-09 model years. We expect that diesel particulate filters (DPFs), also called particulate traps, will be used to meet the new standards on HDDEs beginning in 2007.

The Agency has received information from two heavy-duty engine manufacturers, Caterpillar, Inc. and DaimlerChrysler, indicating that it is technologically necessary to perform the cleaning of uncombusted deposits from DPFs in certain space-constrained truck applications more frequently than at the minimum maintenance interval prescribed for this activity in 40 CFR 86.004-25(b)(4)(iii). These applications use engines in the medium- and heavy-heavy-duty service classes. One reason this minimum interval is included in the regulations is to ensure that the control of emissions in use is not compromised by a manufacturer's overly frequent scheduling of emission-related maintenance. However, § 86.094-25(b)(7)(ii) provides a process by which a manufacturer may request EPA approval of new scheduled maintenance, provided that such requests include supporting data and other substantiation for the recommended maintenance category (emission-related or non-emission-related, critical or non-critical) and for the interval suggested for emission-related maintenance.

The information received from the manufacturers pertains to the technologically necessary maintenance interval only and not to the appropriate maintenance category for DPF cleaning. The Agency has already determined that DPFs (particulate traps) are critical emission-related components (see § 86.004-25(b)(6)(i)(G)). Based on our review of the manufacturers' data, we have established a technologically necessary minimum maintenance interval of 80,000 miles (or 2400 hours) for DPF cleaning on a number of specialty vehicle applications, primarily in the medium-heavy-duty service class. None of these are applications with high sales volumes such as line-haul trucks or heavy-duty pick-up trucks.

The truck applications covered by this notice are those in which the application's purpose imposes severe space constraints on the situating of exhaust system components. The DPF units being designed for use in 2007 vehicles are somewhat larger than the mufflers that they replace, and are sized such that they include sufficient excess filter volume to store the uncombustible ash that normally accumulates between cleanings. There are steps a manufacturer can take to minimize the DPF volume needed for ash build-up, such as through redesigning the engine to burn less lubricating oil, which in turn lowers the oil-derived ash accumulation rate. Our review of the information provided by the manufacturers indicates that they have taken reasonable steps to limit ash build-up through such means, but that the resulting filter volumes are still too large to fit in the space available. However, a modest decrease in the filter volume reserved for ash build-up, made possible through the more frequent scheduling of routine cleaning, results in a DPF small enough to fit in these applications.

Based on a review of the information provided by the manufacturers, we have concluded that the following truck applications have space constraints that warrant this shorter minimum allowable maintenance interval:

  • Beverage truck;
  • Maintenance truck with integral tool boxes;
  • Garbage collection truck with hydraulic packing or picking apparatus;
  • Fire truck;
  • Airport refueler truck with exhaust directed toward the front of the truck;
  • Utility truck with integral tool boxes and outrigger apparatus;
  • Snow plow with under-chassis plow;
  • Dump truck;
  • Concrete mixer truck;
  • Car hauler with integral open racks;
  • Street sweeper;
  • Armored car;
  • Day cab truck (only those for which the entire DPF is located in front of the vertical plane established by the back side of the cab, and which furthermore do not have a rear seat).

Any manufacturer of engines used in applications on this list could make use of this provision. This minimum interval applies only to vehicles with engines in the medium- and heavy-HDDE service classes (that is, with gross vehicle weight ratings above 19,500 lbs); no information was provided establishing such a need in the light-HDDE service class. The functional needs of the applications in this list typically preclude the routing of exhaust systems in a vertical stack or in the space behind the cab outside the frame rails. However, if any model year 2007-09 trucks in this list are in fact designed with a DPF mounted in a vertical stack or in the space behind the cab outside the frame rails, they will not be eligible for the 80,000 mile minimum interval because no case has been established for space limitations in such designs. Also, if an engine family is used in multiple truck applications, some of which are not included in the above list, the engines used in “non-listed” applications are not eligible for the 80,000 mile minimum interval. For these engines the manufacturer must provide the owners with proper maintenance instructions that specify the applicable interval, as required under § 86.087-38.

In addition, to make use of this 80,000 mile minimum maintenance interval, manufacturers must indicate their intention in the applications for certification. They must also state their intent to help ensure that the smaller DPFs will only be installed in the approved truck applications, and must show the reasonable likelihood of the maintenance being performed in use as required under CFR § 86.004-25(b)(6), with consideration given to the shorter specified maintenance interval.

Although the 80,000 mile interval is significantly shorter than the nominal 150,000 mile interval that would otherwise apply, there are a number of factors helping to provide confidence that this maintenance is as likely to be properly performed on schedule. First, the covered vehicle applications are commercial in nature. In general, routine maintenance on commercial vehicles is more likely to be performed on schedule to avoid the costly job delays, customer dissatisfaction, workforce idling, and emergency repairs arising from component failures in the field, and also of course to avoid jeopardizing warranty coverage. Second, many of these vehicles are not typically driven over large distances during the course of a year. As a result, filter cleaning at 80,000 mile (or 2400 hour) intervals is not likely to be so frequent as to irritate vehicle operators or hamper them from accomplishing their daily tasks, which might in turn cause them to neglect the needed cleaning. Third, the continued build-up of ash from a lack of cleaning would increase engine backpressure, resulting in loss of power, poor fuel economy, and eventually vehicle stalling. Commercial vehicle drivers and maintenance technicians are likely to be well aware of these serious consequences from neglected maintenance. Fourth, we expect that most or all manufacturers will provide a visible signal or some similar indication to inform a driver of the need for filter cleaning, thus reducing reliance on manual tracking of vehicle mileage to provide the needed reminder that maintenance is due. Finally, DPF cleaning is covered under the “critical emission-related components” provision of 40 CFR 86.004-25(b)(6). Thus, manufacturers are “required to show the reasonable likelihood of such maintenance being performed in use.” A Start Printed Page 11413number of means are available to make this showing, including the visible signal indication mentioned above.

We are limiting this determination to the 2007-2009 model years for two reasons. First, we believe that the problem of redesigning the covered vehicles to accommodate DPFs, though a matter of technological necessity, arises largely from the time remaining before 2007, which precludes manufacturers performing an extensive redesign of these space-constrained vehicles to accommodate the DPFs. Given more time, the somewhat larger DPFs needed to achieve 150,000 mile cleaning intervals could be accommodated in vehicle designs without compromising mission objectives.

Second, the compliance strategies being chosen by the engine manufacturers generally entail a two step approach to meeting the new NOX standards, such that NOX aftertreatment devices will not be employed until 2010, and engine/vehicle designs will remain stable through the 2007-2009 phase-in period. Although the technology choices for 2010 NOX control have not yet been made, we think it likely that new exhaust system space requirements will be added to those entailed by the use of DPFs in 2007. Given that three additional years of leadtime are available before 2010, and that adjusting the DPF cleaning interval can contribute, at best, only modest relief to these space constraint problems, we expect manufacturers to rely on broader vehicle redesigns rather than on shorter cleaning intervals to resolve any such problems. Should that process identify applications in which shorter DPF cleaning intervals are still technologically necessary for 2010 and later heavy-duty vehicles, we would expect manufacturers to take this up with us in a timely manner.

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Dated: February 27, 2006.

William L. Wehrum,

Acting Assistant Administrator, Office of Air and Radiation.

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[FR Doc. E6-3146 Filed 3-6-06; 8:45 am]