If you operate heavy construction equipment, agricultural machinery, generators, or marine vessels in Washington, off-road diesel — also called red dye diesel — is likely your most cost-effective fuel option. But with lower cost comes specific rules about how it can be used. Misuse carries serious federal and state penalties. Here’s what every Washington operator needs to know.

What Is Off-Road Diesel and Why Is It Cheaper?

Off-road diesel and on-road diesel are chemically the same fuel — both are #2 diesel meeting ASTM D975 specifications. The difference is taxation. On-road diesel is taxed at the federal and state level to fund highway infrastructure (currently approximately $0.244 per gallon federal + $0.336 per gallon Washington state = $0.58+ per gallon in highway taxes). Off-road diesel is exempt from these taxes because the equipment that uses it doesn’t operate on public roads.

To enforce this tax exemption, the IRS requires off-road diesel to be dyed red — specifically with Solvent Red 26 or Solvent Red 164. That red color is how inspectors identify it in the field. The fuel itself performs identically to on-road diesel; only its legal use is restricted.

Who Can Legally Use Red Dye Diesel in Washington?

Off-road diesel is legal for any equipment that does not operate on public roads and highways. This includes:

  • Construction equipment: excavators, bulldozers, scrapers, cranes, compactors, and all other non-road machinery
  • Agricultural equipment: tractors, combines, irrigation pumps, and farm machinery
  • Stationary engines and generators used for power generation
  • Commercial fishing vessels and other marine applications
  • Refrigerated trailers (reefer units) — the reefer engine itself runs on off-road diesel even though the trailer rolls on public roads
  • Mining and quarrying equipment
  • Railroad locomotives

What You Cannot Use Red Dye Diesel For

Off-road diesel cannot be used in any vehicle that operates on public roads — period. This includes pickup trucks, semi-trucks, service vans, and any other licensed highway vehicle. It cannot be used to fuel equipment that moves under its own power between job sites on public roads (a bulldozer on a public highway would need on-road diesel in a fuel carrier, for example — though the machine itself runs on off-road).

The penalty for misuse is substantial: the IRS can assess a penalty of $10 per gallon or $1,000 per violation, whichever is greater, plus back taxes owed. State penalties apply separately. IRS inspectors conduct roadside checks of fuel in diesel vehicles and can test for red dye on the spot.

Sulfur Content: Ultra-Low Sulfur Off-Road Diesel

Since 2010, all non-road diesel fuel sold in the United States must be Ultra-Low Sulfur Diesel (ULSD) — 15 parts per million (ppm) sulfur maximum. This is required for Tier 4 equipment with diesel particulate filters (DPF) and SCR systems. Do not use high-sulfur diesel (500 ppm or 5,000 ppm) in any modern equipment; it will damage emission control components and can void equipment warranties.

All off-road diesel delivered by Evergreen Fuel meets ULSD standards and is appropriate for use in all Tier 4 Final equipment.

Getting Off-Road Diesel Delivered to Your Washington Job Site

Evergreen Fuel & Lubes delivers off-road red dye diesel directly to construction sites, farms, marinas, and commercial facilities throughout Western Washington. Our tanker trucks carry metered deliveries with full documentation for your records. Learn more about our off-road diesel delivery service or request a delivery quote for your operation.