Isuzu Manufacturing Services of America, Inc. 734-455-7595 

46401 Commerce Center Drive 

Plymouth, MI 48170-2473 We’re looking to the future by recycling today. 

December 15, 2010 DET-10-131 

Karl Simon 

Director, Compliance and Innovative Strategies Div 

Office of Transportation and Air Quality 

U.S Environmental Protection Agency 

Ariel Rios Building – MC: 6405J 

1200 Pennsylvania Avenue, N.W. 

Washington, D.C. 20460 

Subject: Request for Approval -- Scheduled Maintenance 40CFR86.1834-01(b)(7) 

 2012-2014MY for _C/D/E_SZXD03.03FA 

Dear Mr. Simon: 

On behalf of Isuzu Motors Limited, Isuzu Manufacturing Services of America hereby request 

that EPA approve as a “new scheduled maintenance” the refill of Diesel Exhaust Fluid (DEF) for 

the Selective Catalytic Reduction (SCR) emission control systems for Isuzu engine families 

CSZXD03.03FA, DSZXD03.03FA, and ESZXD03.03FA. 

This request is for maintenance which did exist on the 2012MY BSZXD03.03FA Isuzu NPR 

Diesel vehicle for which EPA previously approved. The design of that vehicle is to be carried 

over to the 2012MY thru 2014MY and no new technology will be introduced to allow 

maintenance free for useful life. Therefore, the same good engineering judgment is applied 

from the 2011MY. 

-- 

(From DET-10-078 2011MY request) 

The technologically necessary SCR maintenance interval (ie. DEF tank refill interval) is based 

on DEF consumption rate. In determining the recommended DEF tank refill interval, Isuzu 

applied good engineering judgment, as required. It has been determined through durability 

testing that the DEF consumption rate (at worst case) was approximately 2% the rate of diesel 

fuel consumption. At this rate, it would be impossible to equip a vehicle with a DEF tank large 

enough to operate for the standard 120,000-mile maintenance interval without DEF refill. Thus, 

good engineering judgment must be applied to strike a proper balance between the dictates of 

operating the vehicle in commerce and the Agency’s need to ensure emission compliance inuse. 

The following is our substantiation of this request: 

1) Background 

On March 7, 2007, EPA issued a Dear Manufacturer guidance letter (CISD 07-07) 

setting out its SCR vehicle certification requirements for light-duty and heavy-duty 

manufacturers. The guidance addressed 40 CFR §86.004-25, §86.094-25 & §86.1834-

01 Allowable Maintenance; and 40 CFR §86.094-22 & §86.1833-01 Adjustable 

Parameters. 
DET-10-131 

Page 2 of 3 

On February 18, 2009, EPA issued another Dear Manufacturer guidance letter (CISD09-04) providing additional guidance for HD truck manufacturers. The guidance set out 

minimum DEF tank sizes, and allowed a minimum DEF tank size of 2 times the fuel tank 

range if the vehicle is equipped with a DEF tank level indicator (2:1 refill interval). 

2) Reasons for why DEF refill is an emission related, critical maintenance. 

EPA noted in CISD 07-07 that since the SCR catalyst does not function without the use 

of a reducing agent, 40 CFR §86.1834-01(b)(4)(ii)(F) and §86.004-25(b)(4)(iii)(F) would 

apply to the SCR catalyst and all of the associated hardware, including but not limited to, 

the reducing agent, the reducing agent storage tank, the dosing valve, and all lines and 

hoses. We agree with EPA that DEF refill is an emission-related, critical maintenance. 

3) Reasons for why the technologically necessary SCR maintenance interval could be 

based on DEF consumption rate. 

The reasons for why the technologically necessary SCR maintenance interval should be 

the same as EPA found persuasive for determining the 2:1 heavy-duty vehicle DEF refill 

interval. Our vehicles are designed and equipped with a 7.4 gallon DEF tank and a 24.7 

gallon diesel fuel tank. Using the worst case consumption ratio of 2%, this equates to a 

15:1 diesel fuel refill per DEF refill. In terms of mileage this would be approximately 

6,000 miles per DEF refill. 

a) Maintenance is likely to be performed on schedule 

Isuzu has equipped the vehicle with an escalating audible and visual warning chain that 

provides adequate time to refill the DEF. The meter cluster is designed with a constant 

DEF tank level display shown in green, amber, and red indicating urgency to locate DEF 

supply. Also on the meter cluster is a SAE standardized DEF indicator symbol that 

becomes lit and a Message Display Console indicating when the SCR system needs 

attention. 

In the unlikely event that the warnings are not heeded and the maintenance is not 

performed, the performance of the vehicle will be noticeable and significantly degraded. 

Ultimately, if the warnings are not heeded the vehicle will enter a limp mode and would 

require dealer service to restore vehicle to normal operating condition.

b) There is limited space available on our vehicles for a large DEF tank

Our medium duty vehicle is constrained in the amount of space that can be dedicated to 

a DEF tank. A dedicated tank designed to meet the 120k maintenance interval would 

need to be 240 gallons and mounted on top of the frame due to the size and weight. 

This lost cargo carrying space taken up by the tank would limit the body designs 

available and other commercial applications. 

The weight associated with a 240 gallon tank of DEF would be at a minimum of 2180 lbs 

for DEF alone. This greatly reduces the vehicle load carrying capacity and results in 

poor fuel efficiency. With the reduced load carrying capacity, this vehicle would not be 

competitive in the market. 

Mounting the tank to the undercarriage also is not feasible due to the space available. A 

tank of this size would interfere with the exhaust aftertreatment systems and drivetrain 

components. A tank mounted on the side would require a redesign of mounting 

hardware and suspension system to account for the offset weight. 

Appendix A. shows the limited space available. 
DET-10-131 

Page 3 of 3 

c) Limitations based on physical properties of DEF 

Frozen DEF 

Since DEF freezes at -11 °C, the time to thaw a 240 gallon tank that has become frozen 

would take longer than EPA would allow. Using additional heaters would help improve 

the time but it would significantly drive up the cost of the system. 

DEF Storage 

As an industry recommendation, the shelf life of DEF is approximately 1 year under ideal 

storage and environment conditions. Once DEF begins to degrade, its NOx conversion 

effectiveness in an SCR system decreases. Since the average distance our truck driven 

in one year is about 50,000 miles, it would take 2.4 years to meet the 120k mile interval 

at which time DEF degradation would have occurred and lost its effectiveness to reduce 

NOx. The vehicle service lamp within in this time would have been lit and the repair 

would require the drain and refill DEF tank. Therefore, this would negate the purpose of 

designing a tank to meet the 120k mile interval. 

d) DEF public awareness and readily available to drivers 

Numerous press releases and public relations activities have been distributed related to 

the development of DEF infrastructure. Announcements of new truck stops planning to 

add DEF and new industry DEF websites have been released. Typing “diesel exhaust 

fluid” in any internet search engine provides plenty of articles on its use and availability. 

i) DEF is available at dealerships, gas stations, truck stops, and grocery stores 

The manufacturers of SCR vehicles have worked with franchised dealerships to supply 

DEF to their customers. Several of these manufacturers have agreements with gasoline 

station chains to ensure availability of DEF at those refill stations. In addition, several 

truck stops have announced publicly their intention to stock DEF. To further ensure the 

quality of DEF at these retail locations, the American Petroleum Institute will be 

conducting a quality control program with the support of distributor and retailer licensing 

agreements. 

ii) Drivers can locate DEF through locator website 

Isuzu is participating in the DOE/NREL locator website for drivers to use to locate 

supplies of DEF. In addition, Isuzu will setup on its website a dealer locator where DEF 

is available along with an 800 number to assist the driver in emergencies. 

Summary

Based on our good engineering judgment, Isuzu believes our vehicle is designed and equipped 

with the necessary features to ensure the SCR maintenance interval (DEF refill) will be 

completed and meets the emission in use compliance standards. 

If you have any questions or require additional information, please contact me at 734-582-9262 

or Scott Crafard of my staff at 734-582-9250. 

Sincerely, 

Jeffery A. Marsee 

Chief Representative 

Emissions & Safety 

Isuzu Manufacturing Services of America, Inc 

cc: Mr. Murono , ISZJ-F RL3 
Appendix A

DET-10-131

 December 15, 2010