Washington State Department of Ecology

Clean Diesel Grant Program

Frequently Asked Questions

Why should I install diesel emission control technologies?

Diesel engines emit a mixture of fine particles and other pollutants, including more than 40 cancer-causing substances. Seventy percent of the cancer risk from airborne pollutants is from diesel exhaust. Breathing diesel exhaust makes healthy people more at risk for respiratory disease. It worsens the symptoms of people with health problems such as asthma, heart disease, and lung disease.

Emission control technologies effectively reduce or eliminate toxic exhaust and fine particles. Benefits include increased protection for public health in your community and workforce, reduced soiling of buildings, and improved regional visibility.

What types of emission control technologies are funded by the Clean Diesel Grant Program?

The program funds technologies based on the California Air Resources Board (CARB) classification for retrofit technologies, shown in the table below. These technologies reduce 25% to 100% of toxic emissions from the tailpipe, and 100% of emissions from the crankcase. Either the U.S. Environmental Protection Agency (EPA) or CARB verifies emission reductions for all technologies.

Diesel Retrofit Device CARB

Classification Particulate Matter Reduction

Oxidation Catalysts Level 1 Device >25%
Partial Flow Filters Level 2 Device >50%
Particulate Filters Level 3 Device >85%

Do any of the retrofit devices require maintenance?

Some do. Flow-through devices are maintenance-free; however, the most efficient filtration-type devices do require routine maintenance.

Oxidation catalysts and partial flow filters require no maintenance
Particulate filters typically require service annually or every 50,000 miles, whichever comes first. Specialized equipment is required to clean filters. Contracted cleaning services generally cost $100 to $500 per filter, depending on the level of required cleaning. For transit fleets that install five or more filters, the Clean Diesel Grant Program will provide a high-grade particulate filter cleaning machine.
Closed crankcase ventilation filters require service every 500 hours or every oil change, whichever comes first. Several manufactures have recently developed filters that double the filter life. Replacement filters typically cost $40 to $60 per filter.

How long does it take to complete the retrofit process?

Depending on the technology selected, it can take anywhere from six to 18 months to complete the process. Most products are not off-the-shelf items and must be scheduled for manufacture. Emission control devices that require muffler replacement must be sized and fitted similar to the original equipment manufacturer (OEM) muffler.

Tailpipe controls: Although some items may be in stock, most are custom ordered for manufacture. Manufacturers can typically provide product within three to six months, but it may take longer during peak demand periods. Expect a project completion period of 12 to 18 months.
Crankcase controls: While closed crankcase ventilation filters are not a custom order, contractors stock a limited supply of product. Manufacturers can typically provide product within eight to 10 weeks. Expect a project completion period of up to six months.

How long will vehicles be out of service during the retrofitting process?

Contractors work with fleet managers to develop an installation schedule that disrupts fleet operations as little as possible. This may include installing during evenings or on weekends. Contractors generally provide one to two installers per fleet, depending on the size of the fleet. The average installation times are as follows (these times vary depending on the experience of the installer):

Diesel Retrofit Device Time Needed

Oxidation Catalysts and Partial Flow Filters = 1 to 1.5 hours
Particulate Filters = 3 to 4 hours
Closed Crankcase Ventilation Filters = 2 to 3 hours

Will the retrofits void an engine warranty?

No. The Magnuson-Moss Warranty Act ensures that an engine manufacturer cannot void a warranty due to the installation of retrofit emission control technologies. In fact, most engine manufacturers now provide and install retrofit emission control technologies.

How will the engine maintenance affect the performance of retrofit devices?

Engine maintenance will not affect the performance of properly selected retrofit devices. Program technicians and contractors work closely with fleet managers to ensure that retrofit devices are appropriately matched to both the engine specifications and the fleet operations.

Do the fleet mechanics need to be involved in the retrofitting process?

No. The contractors will survey the equipment, select the appropriate retrofit device, and supply and install all products.

Will drivers, mechanics and riders notice a difference in the exhaust?

Most people notice there is significantly less diesel exhaust smell. The amount of change will depend on the device chosen. For many types of vehicles, installing closed crankcase ventilation filters eliminates in-cabin exhaust exposure for both drivers and passengers.

How long must a vehicle remain in my fleet before it qualifies for a retrofit?

Vehicles should remain in the fleet for at least two years.

What happens if an engine blows the seals on a turbocharger?

If a vehicle has a catastrophic failure of a turbocharger or engine, its aftertreatment device will need to be inspected for oil and debris. Any oil residue will need to be removed from the exhaust system.

Diesel Oxidation Catalyst (DOC): Remove the DOC from the vehicle and set the DOC on end to drain excess oil. During startup after repairs, expect a small amount of smoke from the combustion of residual oil. Do a final inspection of the exhaust system before returning the vehicle to service.
Diesel Multi-stage Filters (DMF): Remove the center section, drain as above and air dry.
Diesel Particulate Filters (DPF): Remove the pre-filter section and drain as above. Remove the center filter section, eliminate any debris and inspect for damage. If the center filter section is oil soaked, contact a reputable company to regenerate the filter. If you have questions about servicing DPF units, contact the Department of Ecology Air Quality Program at (360) 407-6863.

What happens if the project is not completed by the project end date?

Projects not completed by the project end date will be extended to ensure completion.

I’m interested in idle reduction technologies to help reduce fuel costs. Are these available and are there restrictions on these purchases?

The Clean Diesel Grant Program recently expanded to include idle reduction technologies for PUBLIC FLEETS ONLY. Because idle reduction technologies conserve fuel and provide a pay-back period to the fleet owner, some awards may require up to 50% matching funds. Ecology will review applications before determining how to purchase selected technologies and if matching funds are required. All purchases must meet the Washington State guidelines for purchasing goods and services.

EPA has verified several types of idle reduction technologies as eligible for use. Fleets will need to review the technologies available and consult with the manufacturer for correct use. More information on these eligible idle reduction technologies is on the EPA SmartWay Technology Program's Verified Idling Reduction Technologies website .

Are there other requirements for eligible vehicles?

Vehicle selected for retrofits must still be operating within engine manufacturers’ specifications. This includes, but is not limited to:

Oil consumption
Engine crankcase blow-by
Fuel system must not be tampered with.

Who do I contact if I have more questions?

Mike Boyer, 360-407-6863 or
Carrol Johnston, 360-407-6568