### Question
Can you define what ultra-low sulfur diesel fuel means?


### Answer
**Ultra-low sulfur diesel fuel** is defined as the following in *42 U.S.C. § 16091*:

> diesel fuel that contains sulfur at not more than 15 parts per million

#### Citation:
  - *42 U.S.C. § 16091*
  - Heading: **CHAPTER 149-NATIONAL ENERGY POLICY AND PROGRAMS > SUBCHAPTER VII-VEHICLES AND FUELS > Part C-Clean School Buses**

