Case Law Update: 10th Gear v. PACCAR — Court Rejects Clean Air Act Preemption of MX-13 Engine Warranty Claim

A federal judge in Washington State has refused to throw out a proposed class action by truck owners who say PACCAR's EPA 2021 MX-13 diesel engines have defective fuel injectors, holding that the federal Clean Air Act does not preempt their claim under PACCAR's Engine Warranty. In 10th Gear LLC v. PACCAR Inc., No. 2:23-cv-01933-RSL (W.D. Wash.), U.S. District Judge Robert S. Lasnik denied PACCAR's motion to dismiss the Third Amended Class Action Complaint in an order dated October 1, 2026. The ruling does not decide whether the engines are defective; it lets the breach of express warranty claim proceed.

What the case is about

According to the court's order, the plaintiffs are thirty-one purchasers and/or lessees of tractor-trailer and vocational trucks equipped with EPA 2021 MX-13 engines. They allege that deposits build up inside the fuel injectors, causing them to skip pilot injection, the first of the three injection events of the combustion cycle. The complaint alleges this produces "engine knocking, severe vibration and a generally rough-running engine," and that the trucks' onboard computers sometimes reduce engine power, which plaintiffs claim can happen without warning and leave a truck "virtually undrivable." These are allegations, not findings.

The plaintiffs also allege that PACCAR promoted temporary measures, such as injector cleaning, fuel additives, software updates, and replacement with similarly designed injectors, and that owners "came in for repair after repair," losing money to downtime and diminished value.

PACCAR's Limited Warranty Agreement includes an Engine Warranty and incorporates a separate Emissions Warranty. As described in the order, the Engine Warranty promises the engine is "free from defects in materials and factory workmanship," with basic coverage for twenty-four months, 250,000 miles, or 6,250 hours, whichever occurs first. The plaintiffs allege PACCAR "frequently covered" injector cleaning and replacement under the Engine Warranty, and that their repair records often list the warranty as "Standard MX Engine" or "Base MX Engine" rather than "Emissions."

PACCAR's argument: federal emissions law controls

PACCAR argued that because the fuel injectors are emissions-related parts, any warranty claim about them is preempted by Clean Air Act § 209(a), 42 U.S.C. § 7543(a), which bars states from adopting or attempting to enforce "any standard relating to the control of emissions from ... new motor vehicle engines." PACCAR also argued that EPA and the California Air Resources Board (CARB) had already addressed the issue by requiring an extended federally mandated warranty.

What the court held

The complaint states a separate Engine Warranty theory. The court wrote that "PACCAR reads the Third Amended Complaint too narrowly." While the plaintiffs do invoke the Emissions Warranty, they also allege that the injector defect harmed how the engine runs and that PACCAR could not repair it. Accepting those allegations as true, the court found the plaintiffs "plausibly plead an Engine Warranty theory based on defects affecting the operation of the engine without regard to whether those same defects also affected emissions compliance."

No express preemption of that theory. The court explained that the federal emissions warranty under Clean Air Act § 207(a), 42 U.S.C. § 7541(a)(1)(B), is tied to defects that cause an engine to fail to conform to emissions regulations, not simply to any defect in an emissions-related part. The court relied on a 2015 New Jersey federal decision involving Caterpillar engines, which distinguished "a failure to perform as an EPA-compliant engine" from "a failure to perform as an engine at all." That decision also held the claim under the federally mandated emissions warranty was preempted, and the court noted that, unlike the Caterpillar plaintiffs, the owners here do allege emissions noncompliance. Even so, the court held: "That the fuel injectors are also emissions-related components does not transform every warranty obligation arising from their malfunction into an obligation imposed by the CAA."

No implied preemption either. The court said the Engine Warranty theory does not require the court or a jury to find that EPA or CARB chose an inadequate emissions remedy, impose a different emissions standard, or order a recall. "It requires only a determination whether PACCAR breached its separate contractual promise to repair Warrantable Failures affecting operation of the engine."

The ruling is expressly limited. In the court's words, "The Court's ruling is limited." It did not decide whether plaintiffs may separately recover under the Emissions Warranty, or whether particular forms of relief, such as a recall or a required injector design, might be preempted. In denying an earlier motion to dismiss, the court had noted that PACCAR "repeatedly agreed that the fuel injector problems are covered by the Basic Engine Warranty."

What this means if you have a vehicle or engine warranty claim

This is a single federal trial-court ruling at the pleading stage in Washington; it does not bind Florida courts and does not predict how this or any other case will end. Still, it highlights practical points for owners facing a recurring defect:

• Identify every warranty that applies. A vehicle can carry more than one written warranty. The court treated the Engine and Emissions Warranties as separate promises.
• Keep every repair order. The plaintiffs pointed to repair records identifying the applicable warranty as "Standard MX Engine" or "Base MX Engine" rather than "Emissions." Labels like these can matter later.
• Document repeat repairs and downtime. The core allegation is a defect repaired again and again without a permanent fix; dates, mileage, symptoms, and downtime document that pattern.
• A regulator-driven fix may not end a contract claim. PACCAR argued that EPA and CARB had already addressed the injector issue by requiring an extended warranty; that argument did not defeat the Engine Warranty claim at this stage. Whether similar reasoning applies elsewhere depends on the facts and the governing law.
• Watch your coverage limits. The Engine Warranty here ran for a set time, mileage, or hour limit, whichever occurred first. Reporting problems in writing while coverage is in effect is generally a sound practice.

For how protection plans differ from a manufacturer's warranty, see What Is a Vehicle Service Contract? More court rulings are collected on our Case Law & Industry Insights page.

Case details

• Case: 10th Gear LLC, et al. v. PACCAR, Inc.
• Court: U.S. District Court for the Western District of Washington
• Case number: 2:23-cv-01933-RSL
• Ruling: Order (Doc. 164) denying PACCAR's motion to dismiss the Third Amended Class Action Complaint and granting plaintiffs' motion to seal, dated and entered October 1, 2026

This article summarizes a court ruling for general informational purposes as of October 16, 2026, and is not legal advice. Reading it does not create an attorney-client relationship. If you have a dispute over a vehicle warranty or service contract, Louis Law Group offers a free case evaluation.