Cold Weather Diesel Reliability Act of 2025

1) WHAT HAPPENED: On March 11, 2026, the Senate Committee on Environment and Public Works held hearings on S.3135, the Cold Weather Diesel Reliability Act of 2025. The bill was introduced by Sen. Dan Sullivan (R-AK) in November 2025 and has 3 cosponsors. The bill is currently in committee markup stage — it has not been voted out of committee, nor has it passed the Senate. The identical companion bill HR6250 sits in the House Energy and Commerce Committee. 2) THE MONEY TRAIL: This bill authorizes ZERO direct appropriations. It creates a regulatory exemption — requiring the EPA to revise existing Clean Air Act regulations to allow manufacturers of on-highway diesel vehicles and nonroad diesel equipment to suspend 'inducement-related engine derate or shutdown functions' that are triggered by emissions control system faults when ambient temperatures are at or below 0°C. The economic benefit is entirely cost-avoidance: reduced warranty claims, fewer service interventions, and lower engineering costs for developing cold-weather DEF mitigation. The vehicle/equipment operator is also a beneficiary through reduced downtime. The bill explicitly restricts this modification to manufacturers only — third parties cannot perform the modifications. 3) STRUCTURAL WINNERS AND LOSERS: The direct beneficiaries are diesel engine OEMs and heavy-duty truck/equipment manufacturers with significant sales in cold regions. PACCAR ($PCAR) builds Kenworth and Peterbilt trucks heavily used in northern states and Canada. Cummins ($CMI) is the leading independent diesel engine supplier for heavy trucks and nonroad equipment. Deere and Caterpillar benefit on the nonroad equipment side — agricultural and construction equipment that operates in sub-freezing conditions. Oshkosh also builds defense and vocational trucks for cold climates. The losers are not directly created by this bill but indirectly: competitors in emissions control aftertreatment components (DEF sensors, DEF tank heaters, SCR catalysts) may see slightly reduced demand for cold-weather aftermarket parts. Environmental advocacy groups oppose the bill as weakening Clean Air Act enforcement. 4) TIMELINE AND LEGISLATIVE PATH: The bill held hearings in March 2026 but has not been voted out of committee. With the 119th Congress entering its second year and midterm elections approaching in November 2026, the legislative window is narrowing. The bill must pass both chambers and be signed by the President. Given the partisan divide on environmental deregulation, passage probability is moderate at best (estimated 35-45%). The companion bill HR6250 moving simultaneously increases odds slightly. No presidential action directly amplifies this bill — the Presidential Determination on Domestic Petroleum Production from April 20, 2026, is broadly supportive of domestic energy infrastructure but does not specifically address diesel emissions or cold-weather reliability.