FMCSA allows gravity-fed auxiliary fuel tanks on trailers

The requirement to apply for an exemption to use gravity-fed or siphon-fed fuel systems on commercial motor vehicles has been withdrawn. FMCSA determined that a final rule published on February 19, 2026, already provides the needed relief. Carriers no longer need to request special permission to install these systems.

The updated regulation allows gravity or siphon feeds for auxiliary equipment under specific conditions. The fuel tank must have a capacity of not more than five gallons. It must be mounted on the trailer chassis frame or trailer bed. The system must supply fuel for purposes other than operating the motor vehicle itself. The equipment may only run when the vehicle is not in motion.

These changes took effect on March 23, 2026. Trucking companies that use trailer-mounted auxiliary equipment can now operate these systems under the new rule. Drivers and fleet managers should verify that their auxiliary fuel setups meet the five-gallon limit and stationary-use requirement.

The agency closed the exemption request as of the effective date. The regulatory amendment applies to all commercial motor vehicles subject to the fuel system requirements. Carriers should update their maintenance and compliance records to reflect the new standard.

Source: Federal Register — https://www.federalregister.gov/documents/2026/07/30/2026-15431/parts-and-accessories-necessary-for-safe-operation-application-for-exemption-renewal-from-charles