An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Verified Technologies for SmartWay and Clean Diesel

Caterpillar Technology—Emissions Upgrade Group (model 3306)

This retrofit technology is included on EPA's Verified Technologies List for Clean Diesel.

On this page:

Technology specifications

Engine Model/Application Caterpillar model 3306 diesel engines for nonroad applications, model years from 1970 to 1995 with mechanical direct fuel injection
Retrofit Fuel, Max Sulfur 500 parts per million (ppm)
Reduction in particulate matter (PM) 22%
Reduction in nitrogen oxide (NOx) 37%
Reduction in hydrocarbons (HC) 71%
Reduction in carbon monoxide (CO) 13%

Top of Page

Criteria to achieve emission reductions

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

Verification Letter from EPA

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.