The available evidence does not support a reliable list of “the nine worst” GM engines. It does document specific concerns in certain vehicles: premature timing-chain wear in named V6 applications, an oil-consumption test and piston-and-ring repair procedure, and AFM lifter repairs for specified 5.3L and 6.2L engines. Those records are useful when checking a particular vehicle, but they do not establish that every engine in a family is defective or rank GM engines by reliability.
Why a nine-engine “worst” list would be misleading
Calling an engine one of GM’s worst requires a clear standard—such as failure frequency, severity, repair cost, or historical impact—and evidence that supports comparing engines by that standard. The available material does not provide comparative failure rates or establish a definitive set of nine engines.
It is also important to distinguish a service bulletin or customer-satisfaction program from a safety recall, investigation, lawsuit, or owner complaint. A bulletin describes a service procedure or condition for specified applications; it is not, by itself, proof of a defect affecting every engine in a family. NHTSA’s technical service bulletin data is not a recall list, and its dataset can include bulletins that do not pertain to a defect.
GM engine concerns documented for specific applications
V6 timing-chain wear in certain vehicles
A February 2011 GM customer notice described a customer-satisfaction program for certain V6-equipped vehicles: 2007 model-year GMC Acadia and Saturn Outlook; 2007–2009 Cadillac CTS, SRX, and STS; and certain 2009 Buick Enclave, Chevrolet Traverse, GMC Acadia, and Saturn Outlook vehicles. The notice said that, under certain driving conditions and extended oil-change intervals, premature timing-chain wear could illuminate the Service Engine Soon light.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minute#1 Best Overall
- Step-by-step procedures written from a complete teardown and rebuild, giving you the confidence to tackle repairs at any skill level.
- Over 700+ clear photos and diagrams that simplify complex systems, helping you complete jobs faster and with fewer mistakes.
- Comprehensive troubleshooting and fault-finding guides to quickly diagnose problems and reduce costly downtime.
GM said oil age and driving conditions could affect wear. Its stated action was to recalibrate the engine control module, including the oil-life monitor. The notice put it this way: “Timing chain wear can be affected by the age of the engine oil and driving conditions.” This describes the covered applications and conditions in that notice; it does not establish a problem in every GM V6 or confirm that a particular vehicle remains eligible for a repair program today.
Oil consumption and piston-and-ring service
GM Bulletin 13-06-01-003E, dated April 2014, describes an oil-consumption test and a piston-and-ring repair procedure when the test meets the bulletin’s stated condition. It also includes timing-chain and balance-shaft-chain work for certain 2010–2011 models built before March 2011.
Rank #2
The bulletin is intended for professional technicians and cautions against assuming its described condition applies to a particular vehicle. It does not, by itself, identify a universal engine-family failure or provide a failure rate. Confirm the exact engine, model year, vehicle application, and bulletin applicability before connecting a vehicle’s oil use to this procedure.
AFM lifter repair procedures for specified V8s
GM Bulletin 15-06-01-002K describes repair procedures for misfire, ticking noise, or malfunction-indicator concerns involving specified 5.3L engine codes L83 and L8B, and 6.2L codes L86, LT1, and LT4, in covered vehicles. The procedures include work on the valve-lifter oil manifold and lifters.
Rank #3
- Detailed repair and maintenance coverage trusted by professional technicians and DIYers for decades.
- Clear step-by-step instructions supported by wiring diagrams, diagnostic charts, and technical illustrations.
- Covers routine maintenance through advanced repairs, making it the go-to resource for keeping your vehicle running reliably.
This supports saying that GM documented a repair concern for certain engine-and-vehicle applications. It does not establish how often the condition occurred or that all engines with those codes fail. The available reproduction is hosted by a third party, so check the current GM service information for the revision and exact vehicle coverage before relying on it for a repair decision.
How to interpret GM’s oil-consumption guideline
GM Bulletin 01-06-01-011P, dated August 2024, gives an accepted oil-consumption rate of 0.946 liter (1 qt) in 3,200 km (2,000 mi) only under stated conditions. The guideline applies to covered 2025-and-prior passenger cars and gasoline-powered light-duty trucks under 8,500 lb GVW when the vehicle is for personal use, under warranty, maintained to schedule, driven non-aggressively, and has less than 58,000 km (36,000 mi). The bulletin also states exclusions involving aggressive driving, high RPM, high speeds, and loaded trucks.
That figure is a service guideline under those conditions—not a measured failure rate, a reliability comparison, or a universal threshold for every GM vehicle. Do not use it alone to decide whether a particular engine is healthy or defective.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What to check before buying or repairing a GM vehicle
- Identify the vehicle precisely. Record the VIN, model year, engine code, and vehicle model. Similar engine displacements or family names do not establish that a bulletin covers the vehicle.
- Check the VIN for current recall information. Use NHTSA and manufacturer resources to check for recalls or other vehicle-specific communications. A bulletin, customer-satisfaction program, and recall have different meanings; do not treat one as proof of another.
- Match any bulletin to the exact application. Confirm the engine code, model year, vehicle, symptoms, and bulletin revision. A procedure for a related engine or a different year may not apply.
- Review maintenance and repair records. For the timing-chain concern, the 2011 notice specifically identifies oil age and driving conditions as relevant. Records can help establish maintenance history, but they cannot by themselves confirm a diagnosis.
- Have symptoms diagnosed before authorizing repairs. A warning light, ticking noise, misfire, or oil use can have more than one cause. The cited procedures are service guidance, not a substitute for a vehicle-specific diagnosis.
What can—and cannot—be concluded
These documents identify real service concerns in defined applications, but they do not rank GM engines or supply the failure-rate data needed to substantiate nine “worst” choices. For a used-car decision, the useful question is whether a particular VIN and engine code fall within a documented concern, what symptoms or service history are present, and whether an applicable repair or recall has been completed.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Quick Recap
Best Value
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
