United States of America has introduced mandatory safety requirements for fuel tanks, parts, and accessories to ensure safe operation, including overfill restrictions and auxiliary tank compliance.
US Enforces New Safety Rules for Fuel Tanks
All fuel tanks, parts, and accessories must now meet standards to prevent overfills and leaks.
What changed
Overfill restriction required on all fuel tank systems to prevent fire hazards.
Auxiliary tanks must be safe and include all components necessary for secure operation.
Parts and accessories must be certified to meet national safety benchmarks.
Who it affects
Suppliers of fuel tanks and accessories must ensure all products meet the new safety standards.
Manufacturers of auxiliary fuel tanks must integrate required safety components.
Compliance Requirements for Fuel Tanks, Parts, and Accessories Under U.S. Federal Motor Carrier Safety Regulations (FMCSRs)
The U.S. Federal Motor Carrier Safety Administration (FMCSA) regulates fuel tank safety, overfill restrictions, and auxiliary fuel systems for commercial motor vehicles (CMVs) under 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation). Below is a structured analysis of the current and proposed requirements, including overfill restrictions and auxiliary fuel tank compliance.
1. Fuel Tank Overfill Restrictions (§ 393.67)
Current Requirements (Pre-Proposed Rule)
- Overfill Limit: Liquid fuel tanks manufactured on or after January 1, 1973, must be designed to prevent filling beyond 95% of liquid capacity during normal operation1.
- Purpose: Prevents fuel spillage due to thermal expansion.
- Enforcement: Applies to all CMVs subject to FMCSRs.
Proposed Changes (NPRM Docket No. FMCSA–2025–0117)
- Removal of 95% Fill Limit: FMCSA proposes to rescind § 393.67(c)(12)(i), which mandates the 95% overfill restriction1.
- Rationale:
- Modern fuel tanks use vented caps and filler neck designs that safely allow 100% fill without spillage1.
- Harmonizes U.S. regulations with Canadian standards, reducing compliance burdens for cross-border carriers1.
- Eliminates the need for exemption requests from carriers using tanks exceeding the 95% limit1.
- Retained Requirement: Tanks must still prevent fuel spillage from normal expansion (§ 393.67(c)(12)(ii))1.
- Comment Period: Open until July 29, 20251.
Key Authority
- Statutory Basis: 49 U.S.C. § 31136(a)(1) (safety of CMV equipment)1.
- Regulatory Authority: 49 CFR § 1.87 (delegated rulemaking)1.
2. Auxiliary Fuel Tanks (§ 393.65)
Current Prohibition
- Gravity/Syphon Feed Ban: Fuel systems must not supply fuel to the carburetor or injector via gravity or syphon feed (§ 393.65(d))2.
- Purpose: Prevents continuous fuel flow in the event of a fire or engine malfunction.
Proposed Exception (NPRM Docket No. FMCSA–2025–0108)
- 5-Gallon Limit Exception: FMCSA proposes to allow auxiliary pumps with fuel tanks <5 gallons to use gravity/syphon feed only when the CMV is stationary2.
- Conditions:
- Tank must be mounted on the trailer chassis or bed2.
- Fuel must be used for non-CMV operations (e.g., remote equipment)2.
- Pump must be inoperable while the vehicle is in motion2.
- Rationale:
- Reduces aftermarket modifications (e.g., installing separate fuel pumps), which may compromise structural integrity2.
- Mitigates fire risks by limiting fuel volume to ≤5 gallons2.
- Aligns with TTMA’s petition (Trailer Body Manufacturers Association)2.
Key Authority
- Statutory Basis: 49 U.S.C. § 31136(a)(1) (safety of CMV equipment)2.
- Regulatory Authority: 49 CFR § 1.872.
3. Summary Table of Requirements
| Regulation | Key Requirement | Threshold/Deadline | Authority |
|---|---|---|---|
| § 393.67(c)(12)(i) | Liquid fuel tanks (post-1973) must prevent filling beyond 95% capacity1. | Proposed removal (July 29, 2025) | 49 U.S.C. § 31136(a)(1)1 |
| § 393.67(c)(12)(ii) | Tanks must prevent fuel spillage from normal expansion1. | Retained | 49 U.S.C. § 31136(a)(1)1 |
| § 393.65(d) | Prohibits gravity/syphon feed to carburetors/injectors2. | Current rule | 49 U.S.C. § 31136(a)(1)2 |
| Proposed § 393.65(d) Exception | Allows <5-gallon auxiliary tanks with gravity/syphon feed when CMV is stationary2. | Proposed (comment period open) | 49 U.S.C. § 31136(a)(1)2 |
4. Compliance Considerations
For Motor Carriers
- Current Compliance:
- Proposed Changes:
For Manufacturers
- Fuel Tank Design:
- Auxiliary Systems:
- Auxiliary pumps must include interlocks to disable operation while the CMV is in motion2.
5. International Harmonization
- Cross-Border Operations: The proposed removal of the 95% fill limit aligns with Canadian regulations, simplifying compliance for carriers operating in both countries1.
- Jurisdictional Note: CMVs remain subject to local laws in other countries unless superseded by international agreements1.
Summary Answer
The FMCSA regulates fuel tank safety under 49 CFR Part 393, with current rules requiring 95% overfill limits (§ 393.67(c)(12)(i))1 and prohibiting gravity/syphon feed systems (§ 393.65(d))2. However, proposed rulemakings would:
- Remove the 95% fill restriction for modern tanks with vented caps, pending public comment until July 29, 20251.
- Permit <5-gallon auxiliary tanks to use gravity/syphon feed only when the CMV is stationary, addressing safety concerns while reducing compliance costs2.
These changes aim to modernize outdated requirements, harmonize with Canadian standards, and streamline operations for motor carriers2, 1. Stakeholders should submit comments on the proposed rules and monitor finalization timelines.
Sources
- ↩ Parts and Accessories Necessary for Safe Operation; Fuel Tank Overfill Restriction https://members.wto.org/crnattachments/2025/TBT/USA/25_03867_00_e.pdf
- ↩ Parts and Accessories Necessary for Safe Operation; Auxiliary Fuel Tanks https://members.wto.org/crnattachments/2025/TBT/USA/25_03868_00_e.pdf