Regulatory Announcement

EPA Sets Standards for Diesel Fluid 

Systems; Adopts Relief Measures for 

Nonroad Equipment 

The U.S. Environmental Protection Agency (EPA) has established 

minimum refill intervals for the diesel exhaust fluid (DEF) used in 

selective catalyst systems to reduce nitrogen oxides (NOx) from diesel 

engines. EPA has also adopted regulatory flexibility for nonroad equipment that can be used during emergency responses. 

Selective Catalytic Reduction Maintenance 

Why is EPA Taking This Action? 

Selective Catalytic Reduction (SCR) is now a common technology in the transportation sector. This technology requires use of a diesel exhaust fluid that reacts in 

the system, is consumed, and must be periodically refilled to sustain control of the 

nitrogen oxides (NOx) emissions. Until now, EPA has been relying on a case-by-case 

approval of refill intervals – regulated as scheduled emission-related maintenance. 

This final rule improves the clarity and transparency of EPA’s requirements, by adding diesel exhaust fluid replenishment to the required emission-related maintenance 

and setting minimum refill intervals. 

What Revisions is EPA Adopting? 

EPA is setting a minimum fluid refill interval of 4,000 miles for light-duty vehicles 

and light-duty trucks that use SCR.1

 For example, a vehicle with a 400 mile fuel 

range would need to refill the DEF tank no more frequently than every tenth fuel fillup. For operators who change oil every 7,500 miles and fill the DEF tank at the time 

of the oil change, no more than one DEF refill would be needed between oil changes. 

This is a shorter interval than we proposed, because oil change intervals are generally 

lengthening, there are trade-offs with the weight of over-sized DEF tanks, and DEF is 

becoming more available to consumers. 

1 Such as a half-ton diesel pickup truck or a diesel SUV 

Office of Transportation and Air Quality 

EPA-420-F-14-017 

July 2014 
Regulatory Announcement

For all heavy-duty engines, EPA is setting a fluid refill interval at least as far (in miles or hours) 

as the vehicle’s fuel capacity. This means the DEF refill must have, at a minimum, a 1:1 ratio 

with the distance between fuel refills. This is the same interval we proposed for engines in 

centrally-fueled vocational trucks, but it is shorter than the 2:1 ratio we proposed for engines 

in long-haul trucks. 

For SCR-equipped nonroad diesel engines, EPA is finalizing a DEF refill interval at least as long 

(in engine-hours) as the vehicle’s fuel capacity, which is unchanged from the proposal. 

Nonroad Engines in Temporary Emergency Situations 

Why is EPA Taking This Action? 

Diesel engines in most modern nonroad equipment are subject to EPA’s technology-forcing 

standards, phasing in through 2015. When routine emission-control maintenance (such as 

DEF refill) does not occur as designed, many engines are set to reduce power to prevent excess 

emissions. For nonroad equipment, this final action allows temporary relief from performancerelated emission control protections, when such equipment is needed to respond to an emergency. 

This will facilitate the use of a variety of nonroad equipment in performing life-saving work 

during rescue and recovery from accidents, floods, hurricanes, and other emergency situations. 

What Revisions is EPA Adopting? 

EPA is adopting revisions that allow manufacturers of nonroad engines to request and EPA to 

approve a new kind of auxiliary emission control device (AECD) as part of the engine certification 

process. This flexibility is intended primarily for new engines used in construction equipment 

and portable equipment used for temporary power generation and flood control. Manufacturers 

will be responsible for activation of any such AECD as well as providing reports to EPA on use 

of these AECD’s. 

Expansion of Emergency Vehicle Provisions 

In June 2012, EPA adopted regulatory flexibility for fire trucks and ambulances, to prevent 

emission-related power loss on these emergency vehicles. On diesel-powered vehicles, when 

emission-related maintenance does not occur as designed, many engines are set to cut power to 

prevent abnormal conditions from causing damage or excess emissions. However, EPA’s 2012 

rule finalized a new kind of AECD so engine manufacturers can have the flexibility to avoid 

such abnormal conditions and avoid reduced performance for fire trucks and ambulances. 

In today’s final action, EPA is expanding the application of this AECD to allow case-by-case 

approval for engines used in other types of emergency vehicles. The intent is to cover vehicles 

that are regularly used in emergency situations, and where the functioning or malfunctioning 

of the standard emission control system may prevent the vehicle from performing as necessary 

when the vehicle is needed to perform work related to reducing risk to human life. 

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Regulatory Announcement

Benefits and Costs of the Rule 

In this action, EPA is providing regulatory certainty that will allow affected manufacturers to 

plan their future product development. The amendments in this action would only have a small 

cost impact for those manufacturers who elect to develop and deploy upgrades to nonroad 

engines as allowed by this rule. EPA does not expect these regulatory changes to have an 

environmental impact. 

For More Information 

You can access the final rule, regulations, and related documents on EPA’s Office of 

Transportation and Air Quality (OTAQ) Web site at: 

www.epa.gov/otaq/hd-hwy.htm 

For more information on this and related rules, please contact the U.S. Environmental 

Protection Agency, Office of Transportation and Air Quality at: 

E-mail: otaq@epa.gov 

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