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2018 CT6 3.6L V6 Burning Oil - Is This Normal or a Known Issue?

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Mike T. · rep 0 · May 25, 2:55 AM · 1 replies · solved · Question

Vehicle: 2018 Cadillac CT6 Luxury 3.6L V6

I've got a 2018 Cadillac CT6 Luxury with the 3.6L V6 engine, and I've noticed it's consuming a significant amount of oil between changes. I'm having to add a quart every 3,000-4,000 miles, sometimes even sooner. There are no visible leaks on my garage floor, and I don't see any blue smoke from the exhaust.

Is this level of oil consumption normal for this engine, or is it indicative of a problem? I've heard some engines can be prone to this. What should I be looking for, and is there a TSB or a specific fix for this issue on the 3.6L V6 in the CT6?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:55 AM

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ClearTheCode admin answer:

Excessive oil consumption in the 3.6L V6 engine, particularly the LGX variant found in your 2018 Cadillac CT6, is a concern that has been reported by some owners. While a minor amount of oil consumption can be considered normal for modern engines, adding a quart every 3,000-4,000 miles is often on the higher side and warrants investigation.

  1. Common Causes for Oil Consumption:
    • PCV System Issues: A clogged or malfunctioning Positive Crankcase Ventilation (PCV) system can lead to increased crankcase pressure, forcing oil past piston rings or valve seals.
    • Piston Ring Design: In some earlier generations of GM's V6 engines, piston ring design or installation tolerances contributed to oil consumption. While the LGX is improved, it's still a potential factor.
    • Valve Guide Seals: Worn or hardened valve guide seals can allow oil to seep into the combustion chamber.
    • Turbocharger Seals (if applicable): If your specific 3.6L V6 variant has turbochargers, worn turbo seals can also contribute to oil consumption, though this is less common without visible smoke.
  2. GM's Stance & TSBs: GM has issued various TSBs over the years regarding oil consumption for different engine families. For the 3.6L LGX, specific TSBs might address PCV system updates or revised engine components. Your dealership can check for any relevant TSBs based on your VIN.
  3. Diagnostic Steps:
    • Oil Consumption Test: A dealership can perform an official oil consumption test, which involves draining, refilling, sealing the oil cap/drain plug, and monitoring oil levels over a specified mileage period. This helps quantify the exact rate.
    • Cylinder Compression/Leak-Down Test: These tests can help identify issues with piston rings or valve seals.
  4. When to See a Shop: You should schedule an appointment with your Cadillac dealership or a trusted independent mechanic. While not immediately catastrophic, excessive oil consumption can lead to premature wear on engine components, catalytic converter damage, and potential engine failure if oil levels drop too low. Early diagnosis is key to identifying the root cause and preventing more severe problems.
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