Responding to the surge in diesel fuel prices, federal and state lawmakers introduced temporary measures intended to provide economic relief. These actions raise questions about fuel use requirements and fuel taxation. “Temporary relief measures may help reduce operating costs, but diesel users should not assume that all diesel fuels are interchangeable,” said Allen Schaeffer, executive director of the Engine Technology Forum. “Understanding which fuel is appropriate for a particular engine and complying with tax and regulatory requirements can help avoid equipment damage, unnecessary maintenance costs, warranty concerns, and compliance issues.” Texas and Alaska get ULSD exemptions Ultra-low sulfur diesel (ULSD) is the standard diesel fuel used for both on-highway and off-highway applications throughout the United States, and it is regulated to a maximum sulfur content of 15 parts per million (ppm). On Oct 5, Texas was granted a waiver to supply diesel fuel with up to 500 ppm of sul