Jump to main content or area navigation.

Contact Us

National Clean Diesel Campaign (NCDC)

Working Together for Cleaner Air

Caterpillar, Inc. Retrofit Technologies

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Caterpillar's Diesel Particulate Filter (DPF)
Verification Letter (PDF)  (2 pp, 110K, June 2005)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%) †
PM NOx HC CO
Diesel Particulate Filter Nonroad, 4-cycle, non-EGR equipped, model year 1996-2005, turbocharged engines with power ratings 130 ≤ KiloWatts < 225 (174.2 ≤ Horsepower < 301.5) 30 89 n/a 93 90

† Baseline assumes an unmodified engine running on 15 ppm sulfur fuel.

The following operating criteria must be met in order for appropriately retrofitted engines to achieve the above emissions reductions:

  1. The engine must be operated with a fuel that contains a sulfur content of no more than 30 ppm.
  2. The DPF requires an exhaust temperature of 260° C for 40% of the cycle for NOx:PM ratios of less than or equal to 20:1 and for NOx:PM ratios equal to or greater than 25:1, only 200° C for 40% of the cycle is required. (As there may be significant variations from application to application, Caterpillar will review actual vehicle operating conditions and perform temperature data-logging prior to retrofitting a vehicle with their PM filter system to ensure compatibility.)
  3. Caterpillar will install a backpressure monitor and high pressure indicator light on all vehicles equipped with this DPF.
  4. The engine should be well maintained and not consume lubricating oil at a rate greater than that specified by the engine manufacturer. Crankcase oil burning systems may not be used with this product.

Caterpillar has indicated there is a negligible (approximately 1 percent) fuel economy penalty with the use of this technology.

Top of page


Caterpillar's Emissions Upgrade Group
Verification Letter (PDF)  (6 pp, 1MB, December 2011)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO
Emissions Upgrade Group Caterpillar model 3306 diesel engines for nonroad applications with model years from 1970 to 1995 with mechanical direct fuel injection. 500 22 37 71 13

The following criteria must be met in order for appropriately retrofitted engines to achieve the emissions reductions:

  1. The Caterpillar Emissions Upgrade Group includes the components necessary to upgrade Caterpillar model 3306 diesel engines with certain machine models and engine arrangements to achieve US EPA Nonroad Tier 1 emissions levels. The primary components are the turbocharger, fuel pump/governor, fuel injection nozzles, and pistons/rings/liners.
  2. Prior to installation, the Caterpillar dealer must determine eligibility of the 3306 EUG by confirming the engine serial number with the engine arrangement and machine model as listed in the Attachment A of the verification letter dated December 15, 2011.
  3. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary Tier 1 components installed and has been tested to ensure the proper fuel delivery, power, torque and speed. The dealer must submit a validation form to Caterpillar to receive a label for the upgraded engine.
  4. Caterpillar will confirm the engine upgrade with the validation submitted by the dealer and issue an engine label which must be installed by the dealer.
  5. For replacement engine upgrades, Caterpillar must comply with the provisions in accordance with 40 CFR 1068.240 for replacement engines.

Top of page


Caterpillar's Emissions Upgrade Group
Verification Letter (PDF)  (3 pp, 800K, May 22, 2012)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO CO2
Emissions Upgrade Group Caterpillar model 3406 diesel engines for nonroad applications with model years from 1973 to 1995 with mechanical direct fuel injection. 15 Tier 1 Level (nonroad) n/a 1

1The CO2 level of reduction was found to be statistically insignificant at this time.

This technology is approved for CAT 3406 engines between 150 and 450 kW, originally manufactured between 1973 and 1995 model years (see Attachment A for detailed list). The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The CAT 3406 EUG includes the components necessary to upgrade Caterpillar model 3406 diesel engines from 1973-1995, 150-450 kW to achieve US EPA Nonroad Tier 1 emissions levels. The primary components are the turbocharger, fuel pump/governor, fuel injection nozzles, pistons/rings/liners, and jacket water aftercooler.
  2. Prior to installation, the Caterpillar dealer must determine eligibility of the 3406 EUG by confirming the engine serial number with the engine arrangement and machine model as listed in Attachment A of this letter.
  3. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary Tier 1 components installed and has been tested to ensure the proper fuel delivery, power, torque and speed. The dealer must submit a validation form to Caterpillar to receive a label for the upgraded engine.
  4. Caterpillar will confirm the engine upgrade with the validation submitted by the dealer and issue an engine label which must be installed by the dealer.
  5. For replacement engine upgrades, Caterpillar must comply with the provisions in accordance with 40 CFR 1068.240 for replacement engines.
  6. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.

Top of page


Caterpillar 3512 Marine Engine Emissions Upgrade Group Kit #1 (MUI to EUI)
Verification Letter (PDF)  (2 pp, 700K, April 2012)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO CO2
Marine Engine Emissions Upgrade Group Kit #1 (MUI to EUI) Caterpillar 3512 diesel engines for non-road, marine applications, model year 1994 – 2006 with mechanical direct fuel injection 15 35 35 18 60 4.5

† The CO2 level of reduction is based on a laboratory E3 general marine engine test cycle; the level of reduction may vary under different conditions.

Please read the information at the end of this page about EPA’s 2008 Locomotive and Marine Engine Regulations

This technology is approved for Caterpillar 3512 unregulated MUI marine variable speed propulsion engines with rated power greater than 600 horsepower originally manufactured between 1994 and 2006 model years. Please note that the level of reduction is based on the ISO 8178 E3 general marine duty cycle. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The Caterpillar 3512 Marine Engine EUG Kit #1 includes components necessary to upgrade Caterpillar model 3512 diesel engines with model years 1994 through 2006 from MUI to EUI engines. The primary critical components are the electronic control module, cylinder packs, oil cooler, turbocharger, fuel injectors, and after-coolers if applicable.
  2. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary EUI components installed and has been tested to ensure the proper fuel delivery, power, torque and speed. The dealer must submit a validation form to Caterpillar in order to receive a label for the upgraded engine.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. This verification is for engines used in vessels with variable speed propulsion systems and is not applicable for engines used in recreational or constant speed propulsion applications.

Top of page


Caterpillar 3500 Marine Engine Emissions Upgrade Group Kit #2 (MUI to Tier 1)
Verification Letter (PDF)  (2 pp, 700K, April 2012)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO CO2
Marine Engine Emissions Upgrade Group Kit #2 (MUI to Tier 1) Caterpillar 3508, 3512, and 3516 (large cam bore) diesel engines for non-road, marine applications, model year 1994 – 2006 15 45 Tier 1 Level (marine) 28 65 3

† The CO2 level of reduction is based on a laboratory E3 general marine engine test cycle; the level of reduction may vary under different conditions.

Please read the information at the end of this page about EPA’s 2008 Locomotive and Marine Engine Regulations

This technology is approved for Caterpillar 3500 Series MUI marine variable speed propulsion engines with rated power greater than 600 horsepower originally manufactured between 1994 and 2006 model years. Please note that the level of reduction is based on the ISO 8178 E3 general marine duty cycle. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The Caterpillar 3500 Marine Engine EUG Kit #2 includes components necessary to upgrade Caterpillar model 3508, 3512, and 3516 diesel engines with model years 1994 through 2006 from MUI to Tier 1 emission levels. The primary critical components are the electronic control module, cylinder packs, oil cooler, turbocharger, fuel injectors, and after-coolers if applicable.
  2. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary components installed and has been tested to ensure the proper fuel delivery, power, torque and speed. The dealer must submit a validation form to Caterpillar in order to receive a label for the upgraded engine.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. This verification is for engines used in vessels with variable speed propulsion systems and is not applicable for engines used in recreational or constant speed propulsion applications.

Top of page


Caterpillar 3500 Marine Engine Emissions Upgrade Group Kit #3 (MUI to Tier 2)
Verification Letter (PDF)  (2 pp, 700K, April 2012)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO CO2
Marine Engine Emissions Upgrade Group Kit #3 (MUI to Tier 2) Caterpillar 3508, 3512, and 3516 (large cam bore) diesel engines for non-road, marine applications, model year 1994 – 2006 15 Tier 2 Level (marine) 3

† The CO2 level of reduction is based on a laboratory E3 general marine engine test cycle; the level of reduction may vary under different conditions.

Please read the information at the end of this page about EPA’s 2008 Locomotive and Marine Engine Regulations

This technology is approved for Caterpillar 3500 Series MUI marine variable speed propulsion engines with rated power greater than 600 horsepower originally manufactured between 1994 and 2006 model years. Please note that the level of reduction is based on the ISO 8178 E3 general marine duty cycle. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The Caterpillar 3500 Marine Engine EUG Kit #3 includes components necessary to upgrade Caterpillar model 3508, 3512, and 3516 diesel engines with model years 1994 through 2006 from MUI to Tier 2 emission levels. The primary critical components are the electronic control module, cylinder packs, oil cooler, turbocharger, fuel injectors, and after-coolers if applicable.
  2. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary components installed and has been tested to ensure the proper fuel delivery, power, torque and speed. The dealer must submit a validation form to Caterpillar in order to receive a label for the upgraded engine.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. This verification is for engines used in vessels with variable speed propulsion systems and is not applicable for engines used in recreational or constant speed propulsion applications.

Top of page


Caterpillar Locomotive Selective Catalytic Reduction (SCR) System
Conditional Verification Letter (PDF)  (3 pp, 500K, December 19, 2012)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO
Caterpillar Locomotive Selective Catalytic Reduction System (SCR) System Caterpillar 3516, heavy duty, line-haul locomotive engine; originally manufactured to meet Tier 2 standards for model years 2010–2011 and remanufactured to meet Tier 1+ standards for model years 2012–2013; turbocharged with power ratings 2650 ≤ Horsepower ≤ 3005 15 10 75 90 70

The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The locomotive must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  2. The locomotive must always have a supply of Diesel Exhaust Fluid (DEF) that meets and displays certification of the American Petroleum Institute ISO Standard 22241-1 quality requirements that ensures the proper purity and concentration of 32.5 percent of urea. The engines and locomotives must be designed to track and log, in nonvolatile computer memory , all incidents of engine operation with inadequate DEF injection or DEF quality.
  3. The SCR system shall not be sold or operated in geographic areas where the DEF may freeze (-11°C), unless it is equipped with tank heaters and DEF line heaters to prevent freezing.
  4. To ensure the appropriate DEF is purchased, the customer is required to maintain DEF purchase receipts and refill records and make them available to Caterpillar upon request. DEF usage log and mileage records will be collected and analyzed by Caterpillar on a semi-annual basis.
  5. Caterpillar is required to provide the operator with clear and visible instructions for maintaining DEF for proper system operation.
  6. Each installation will be equipped with a monitoring system that displays warning lights visible to the operator and audible alarms for low DEF tank level, high SCR inlet temperature and system abnormalities. The monitoring system will also store diagnostic error codes related to DEF tank level and system malfunctions.
  7. The engine exhaust temperature must achieve at least 240°C for 40 percent of operation and not exceed 550°C. Caterpillar will review actual locomotive operating conditions and perform temperature data-logging prior to retrofitting a locomotive with the Caterpillar Locomotive SCR System to ensure compatibility. In the event that a locomotive’s application and/or duty cycle changes, temperature data-logging must be repeated to confirm that the engine exhaust temperature still meets the above criteria.
  8. The Caterpillar Locomotive SCR System may require replacement if SCR inlet temperature exceeds 550°C for an extended, continuous period of time. Operation with temperatures above 550°C may require inspection for damage by Caterpillar.
  9. The Caterpillar Locomotive SCR catalyst should be replaced after 15,000 hours of operation or when the locomotive is rebuilt/remanufactured, whichever comes first.
  10. Caterpillar is responsible for informing customers, in writing, that disposal of the Caterpillar Locomotive SCR System must be in accordance to all applicable federal, state, and local laws.

† - Non-volatile storage is computer memory that can retain stored information even when not powered.

Top of page


Caterpillar 3500 Marine Engine Emissions Upgrade Group Kit #4
Verification Letter (PDF) (3 pp, 744K, June 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO

Marine Engine Emissions Upgrade Group Kit #4

(EUI to Tier 1)
Caterpillar 3508, 3512, and 3516 (large cam bore) diesel engines for non-road, marine applications, model year 1994 – 2006, originally equipped with electronic unit injection (EUI) and rated at 1600 or 1800 rpm 15 Tier 1 Level (marine) – NOx only

Caterpillar has indicated there is an approximately 1 percent fuel economy penalty with the use of this technology.

Please read the information at the end of this page about EPA’s 2008 Locomotive and Marine Engine Regulations

This technology is approved for Caterpillar 3500 Series EUI marine variable speed propulsion engines with rated power greater than 600 horsepower originally manufactured between 1994 and 2006 model years rated at 1600 and 1800 rpm. Please note that this verification is based on the ISO 8178 E3 general marine duty cycle only. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary components installed and has been tested to ensure the proper fuel delivery, power, torque and speed.  The dealer must submit a validation form to Caterpillar in order to receive a label for the upgraded engine.
  2. The original Caterpillar 3500 Series Marine Engine must be equipped with electronic unit injection (EUI), and the electronic control module (ECM) must be replaced or updated as part of the upgrade. The primary critical new components are turbocharger, fuel pump/governor, nozzles, cylinder packs, jacket water after-cooler, and other installation parts as necessary.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. This verification is for engines used in vessels with variable speed propulsion systems and is not applicable for engines used in recreational or constant speed propulsion applications.

Top of page


Caterpillar 3500 Marine Engine Emissions Upgrade Group Kit #5
Verification Letter (PDF) (3 pp, 740K, June 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO
Marine Engine Emissions Upgrade Group Kit #5 (EUI to Tier 2) Caterpillar 3508, 3512, and 3516 (large cam bore) diesel engines for non-road, marine applications, model year 1994 – 2006, originally equipped with electronic unit injection (EUI) and rated at 1600 rpm 15 Tier 2 Level (marine)

Caterpillar has indicated there is approximately up to 2 percent fuel economy penalty with the use of this technology.

Please read the information at the end of this page about EPA’s 2008 Locomotive and Marine Engine Regulations

This technology is approved for Caterpillar 3500 Series EUI marine variable speed propulsion engines with rated power greater than 600 horsepower originally manufactured between 1994 and 2006 model years rated at 1600 rpm. Please note that this verification is based on the ISO 8178 E3 general marine duty cycle only. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary components installed and has been tested to ensure the proper fuel delivery, power, torque and speed.  The dealer must submit a validation form to Caterpillar in order to receive a label for the upgraded engine.
  2. The original Caterpillar 3500 Series Marine Engine must be equipped with electronic unit injection (EUI), and the electronic control module (ECM) must be replaced or updated as part of the upgrade. The primary critical new components are turbocharger, fuel pump/governor, nozzles, cylinder packs, jacket water after-cooler, and other installation parts as necessary.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. This verification is for engines used in vessels with variable speed propulsion systems and is not applicable for engines used in recreational or constant speed propulsion applications.

Top of page


Caterpillar 3500 Marine Engine Emissions Upgrade Group Kit #6
Verification Letter (PDF) (3 pp, 852K, June 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO
Marine Engine Emissions Upgrade Group Kit #6 (Tier 1 to Tier 2) Caterpillar 3508, 3512, and 3516 (large cam bore) diesel engines for non-road, marine applications, model year 1994 – 2006, Tier 1 engine and rated at 1200, 1600, or 1800 rpm (varies by model) 15 Tier 2 Level (marine)

Caterpillar has indicated there is an approximately 1 percent fuel economy penalty with the use of this technology.

Please read the information at the end of this page about EPA’s 2008 Locomotive and Marine Engine Regulations

This technology is approved for Caterpillar 3500 Series Tier 1 marine variable speed propulsion engines with rated power greater than 600 horsepower originally manufactured between 1994 and 2006 model years and rated at 1200, 1600 or 1800 rpm. Please note that this verification is based on the ISO 8178 E3 general marine duty cycle only. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The servicing dealer must follow specific installation instructions approved by Caterpillar and validate that the upgraded engine has the necessary components installed and has been tested to ensure the proper fuel delivery, power, torque and speed.  The dealer must submit a validation form to Caterpillar in order to receive a label for the upgraded engine.
  2. The original Caterpillar 3500 Marine Engine must be a certified Tier 1 engine and the electronic control module (ECM) must be replaced or updated as part of the upgrade. The primary critical new components are turbocharger, fuel pump/governor, nozzles, cylinder packs, jacket water after-cooler, and other installation parts as necessary.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. This verification is for engines used in vessels with variable speed propulsion systems and is not applicable for engines used in recreational or constant speed propulsion applications.

Top of page


EPA’s 2008 Locomotive and Marine Engine Regulations

Vessel owners who use these Marine EUG Kits must be made aware of EPA’s 2008 Locomotive and Marine Engine Regulations which cover existing marine diesel engines that are upgraded, remanufactured, or rebuilt. This mandated measure, referred to as EPA’s Marine Remanufacture Program, requires a vessel owner to use an EPA certified remanufacture system at the time of engine upgrade, of a specific marine engine, if available. Caterpillar is obligated to inform vessel owners if any certified remanufacture system is available for their engine. If not, and the criteria listed is met, then any of the verified 3500 Marine Engine EUG Kits can be applied. If a certified remanufacture system exists, then this verified technology does not qualify for EPA grant funding, and the owner must use a certified system in accordance with applicable regulations. More information about EPA’s Marine Remanufacture Program.

Top of page

For questions, technical assistance, or more information: Contact Us

Jump to main content.