GM Oil Cooler Lawsuit, Silverado HD and Sierra HD Owners Accuse GM of Hiding Duramax Defect
A new proposed class action accuses General Motors of selling certain heavy-duty Chevrolet Silverado and GMC Sierra diesel trucks with an engine oil cooler that can crack, allowing oil and coolant to mix or oil to leak out, which can lead to serious engine damage. The lawsuit was filed on September 24, 2026, in federal court in Michigan. GM has not been found liable, and the allegations are unproven.
This is a newly filed putative (proposed) class action. There is no settlement, no certified class, no claim form and no claim deadline. It is also not a recall. Do not pay anyone claiming to accept “GM oil cooler lawsuit claims.”
GM Oil Cooler Lawsuit Quick Facts
| Detail | Information |
| Case | Hubof v. General Motors, LLC |
| Case number | 2:26-cv-13622 |
| Court | U.S. District Court, Eastern District of Michigan |
| Judge | Robert J. White (Magistrate Judge David R. Grand) |
| Filed | September 24, 2026 |
| Plaintiff | Robert Hubof |
| Defendant | General Motors, LLC |
| Type | Proposed class action. The docket classifies it as a motor-vehicle product liability case. Jury demanded |
| Alleged affected trucks | 2024-2026 Chevrolet Silverado 2500HD and 3500HD and GMC Sierra 2500HD and 3500HD with the 6.6L Duramax diesel engine. The complaint also alleges some 2027 models may be affected |
| Alleged defect | The engine oil cooler can crack, allowing oil and coolant to mix or oil to leak, causing loss of lubrication and possible engine failure |
| Claims described | Breach of warranty, fraudulent concealment, unjust enrichment and state consumer protection claims |
| Proposed class | Nationwide class of purchasers and lessees, with state subclasses |
| Class certified | No |
| Settlement | None |
| Official settlement website | None. There is no settlement |
| Claim form | None |
| Claim deadline | None |
What Does the Lawsuit Allege?
According to the complaint as reported, the oil cooler on the affected trucks is not durable enough and can crack under normal driving conditions such as pressure, heat cycling and vibration. When that happens, the complaint says, pressurized engine oil can enter the cooling system or leak out of the truck. The engine can then lose the oil it needs for lubrication, which can lead to overheating, loss of power, engine seizure or catastrophic failure.
The complaint also alleges that failures happened at relatively low mileage, that repairs can cost tens of thousands of dollars, and that replacement parts have been on backorder and may have the same design problem.
These are allegations, not findings. No court has decided any of them.
Which Trucks Are Named?
The complaint focuses on:
- 2024-2026 Chevrolet Silverado 2500HD and 3500HD
- 2024-2026 GMC Sierra 2500HD and 3500HD
- Trucks equipped with the 6.6L Duramax diesel engine
Some reports describe the class as running through model year 2027, based on the complaint’s allegation that later models may be affected. The lawsuit does not cover gasoline engines. Owners should not assume that every Silverado or Sierra is affected, and the court has not decided which vehicles, if any, belong in a class.
Did GM Know About It?
The plaintiff alleges GM knew of the problem from at least August 2024, when it issued an “urgent” service update about possible coolant contamination on 2024 trucks, and through warranty and repair data, parts sales, dealer reports, safety complaints and owner forums. According to reports on the complaint, it also cites a March 2025 GM service bulletin saying oil in coolant may be caused by a leaking oil cooler.
The lawsuit alleges that GM kept marketing the trucks as reliable while limiting warranty coverage, in some cases blaming “insufficient oil maintenance” for oil loss that the plaintiff says the defect caused. A service bulletin does not by itself prove that GM legally concealed a defect. That is for the court to decide.
What Happened to the Plaintiff?
According to reports on the complaint, Robert Hubof bought a new 2024 Silverado 2500HD in December 2023. At about 16,453 miles in June 2025, he says he heard a loud bang, found oil in the coolant reservoir and oil leaking under the truck, and was later told the cooling system contained oil and metal debris. He says GM did not cover the repair under warranty and quoted him $41,319.79. These details come from the complaint as reported and were not independently confirmed. The estimate is the plaintiff’s repair quote. It is not an amount GM has been ordered to pay or a payout for other owners.
Is It a Recall?
No. A lawsuit is not a recall. No recall tied to this alleged defect has been reported. To check your truck, enter your VIN on GM’s recall lookup or NHTSA’s recall site, and ask a dealer about open service updates.
Is This a Different Case From Earlier GM Duramax Lawsuits?
Yes. Earlier GM Duramax litigation involved different parts and years. For example, the Bosch CP4 fuel pump class action over 2011-2016 diesel trucks ended in a $50 million settlement that received final approval in May 2025. That case has nothing to do with the oil cooler claims here, and GM has issued other service programs for oil cooler lines on different trucks. Don’t assume a claim or recall for one problem applies to another.
Can Owners Join or File a Claim?
No claim form exists. No class has been certified, and nothing has settled. If the court certifies a class or the parties settle, eligible owners would receive instructions through a court-approved notice process.
What Could Owners Receive?
Nothing is guaranteed. The case could be dismissed, narrowed, certified, settled or litigated to judgment. The lawsuit seeks damages and other relief, but no amount can be predicted.
What Should Truck Owners Do Now?
If your truck has an oil or coolant problem:
- Keep your VIN, purchase or lease papers and maintenance records.
- Keep repair orders, diagnostic reports, invoices and estimates.
- Photograph oil in the coolant, leaks or damage, if safe.
- Keep all messages with GM and the dealer, including any warranty denial.
- Have a qualified technician diagnose the problem. Oil in coolant does not prove the defect alleged here.
- Ask your dealer about warranty coverage, and check state lemon laws, which may apply after repeated failed repairs.
- Report problems to NHTSA at nhtsa.gov.
Stop driving a truck that shows low oil pressure, overheating or oil in the coolant, since continued driving can cause more damage.
What Happens Next?
GM must respond to the complaint, which could include a motion to dismiss. If the case continues, the court may address discovery and a class certification decision. As of the docket entries available at filing, only the complaint, a summons and attorney appearances had been recorded. Check PACER for updates.
Key Dates
| Date | Event |
| December 2023 | Plaintiff says he bought a new 2024 Silverado 2500HD |
| August 2024 | GM service update on coolant contamination, cited in the complaint |
| March 2025 | GM service bulletin on oil in coolant, cited in the complaint |
| June 2025 | Plaintiff’s alleged oil cooler failure |
| September 24, 2026 | Lawsuit filed |
| Not applicable | No settlement or claim deadline exists |
Frequently Asked Questions
Is there a GM oil cooler class action?
Yes. Hubof v. General Motors, LLC, No. 2:26-cv-13622, was filed September 24, 2026, in the Eastern District of Michigan.
Which trucks are involved?
Certain 2024-2026 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD trucks with the 6.6L Duramax diesel, with some 2027 models alleged to be affected.
What is the alleged defect?
An oil cooler that can crack, letting oil and coolant mix or oil leak out.
Is there a settlement or claim form?
No.
Is it a recall?
No. Check your VIN with GM and NHTSA.
Has GM been found liable?
No. The allegations are unproven.
How much did the plaintiff’s repair quote say?
The complaint, as reported, says $41,319.79. That is not a payout for other owners.
Is this the same as the CP4 fuel pump lawsuit?
No. That case involved different parts and years and has already settled.
Related Reading
- GM Silverado, Sierra Transmission Lawsuit: Were You Affected?: a separate GM truck lawsuit about transmissions.
Legal information disclaimer: AllAboutLawyer.com is a U.S. consumer legal information website. It is not a law firm and does not provide legal advice. The allegations come from a complaint and have not been proven. This article will be updated if the court docket changes.
Sources
- U.S. District Court, Eastern District of Michigan, docket for Hubof v. General Motors, LLC, No. 2:26-cv-13622 (via Justia Dockets). https://dockets.justia.com/docket/michigan/miedce/2:2026cv13622/398380
- Complaint in Hubof v. General Motors, LLC, filed September 24, 2026, as summarized in reports (the complaint itself was not retrieved).
- Court records and reports on the CP4 fuel pump settlement, final approval May 6, 2025. https://www.hbsslaw.com/cases/cp4-fuel-pump-defect-gm
About the Author
Israr Ahmad is a legal content researcher with 4+ years of experience covering class action settlements and consumer rights cases. He has researched and published coverage of 2,500+ settlements using verified court records, settlement administrator filings, and government sources. Learn more about Israr.