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Excessive Oil Consumption on 2018 Forester 2.5i

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Mike T. · rep 0 · May 22, 3:20 AM · 1 replies · solved · Question

Vehicle: 2018 Subaru Forester 2.5i Premium

I own a 2018 Subaru Forester 2.5i Premium with about 70,000 miles. For the past year or so, I've noticed that I'm adding a quart of oil every 1,500-2,000 miles. There are no visible leaks under the car, and I don't see any blue smoke from the exhaust, so I'm pretty sure it's not leaking externally or burning excessively in a way that's obvious.

I've heard that some Subaru engines, particularly the FB series, have a reputation for oil consumption. Is this normal for my model year, or should I be concerned? What steps can I take to diagnose this, and what are my options if it's a known issue? I'm trying to avoid a major engine repair if possible.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:20 AM

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ClearTheCode admin answer:

Excessive oil consumption has been a concern for some Subaru FB series engines, including those found in the 2018 Forester. While a small amount of oil consumption is normal for any engine, adding a quart every 1,500-2,000 miles is generally considered higher than acceptable.

  1. Perform an Oil Consumption Test: The first step is to have a Subaru dealership or independent shop perform an official oil consumption test. This involves topping off the oil, sealing the dipstick and fill cap, and having you return after a specified mileage (e.g., 1,200 miles) to measure the exact amount of oil consumed.
  2. Check for PCV System Issues: A clogged or faulty PCV (Positive Crankcase Ventilation) valve can contribute to oil consumption by not properly venting crankcase pressure, leading to oil being drawn into the intake.
  3. Review TSBs and Warranty: Subaru has addressed oil consumption issues with TSBs and extended warranties for certain engine components (like piston rings) in specific model years. Check if your VIN falls within any affected ranges.

Common Causes:

  • Piston Ring Design: In some FB engines, the design of the oil control piston rings was found to be insufficient, leading to oil bypassing the rings and being burned in the combustion chamber.
  • PCV Valve Malfunction: A stuck or clogged PCV valve can cause pressure imbalances that force oil past seals or into the intake.
  • Valve Guide Seals: Worn valve guide seals can allow oil to seep into the combustion chambers.

When to See a Shop:

  • You should schedule an oil consumption test with a Subaru dealership. This is crucial for documenting the issue and determining if you qualify for any warranty repairs or assistance. If the consumption is confirmed as excessive, the repair often involves replacing the piston rings, which is a significant engine job. Addressing it promptly can prevent potential long-term issues like catalytic converter damage from oil ash.
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