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2017 Forester 2.5i Burning Oil - Is this normal or a known issue?

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Nicole W. · rep 0 · May 22, 3:21 AM · 1 replies · solved · Question

Vehicle: 2017 Subaru Forester 2.5i Premium

I have a 2017 Subaru Forester 2.5i Premium with about 90,000 miles on it. Lately, I've noticed I'm adding a quart of oil every 1,500-2,000 miles. There are no visible leaks under the car, and no smoke from the exhaust that I can see.

I've been diligent with oil changes using the recommended synthetic oil. My previous cars never consumed oil like this, so it's a bit alarming. I'm worried about potential long-term damage to the engine or catalytic converter.

Is this level of oil consumption considered "normal" for these FB engines, or should I be concerned? What steps can I take to diagnose this, and what might be the potential causes?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:21 AM

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ClearTheCode admin answer: Excessive oil consumption in certain Subaru FB series engines, including the 2.5i in your 2017 Forester, has been a documented concern for some owners. While a small amount of oil consumption is normal for any engine, adding a quart every 1,500-2,000 miles is generally considered high and warrants investigation.

Here's a breakdown of potential causes and steps:

  1. Common Causes for Excessive Oil Consumption:

    • Piston Rings: The most common culprit in affected FB engines has been issues with the design or material of the piston oil control rings, leading to oil bypassing into the combustion chamber.
    • PCV (Positive Crankcase Ventilation) System: A faulty PCV valve or clogged PCV system can lead to increased crankcase pressure, forcing oil past seals or into the intake.
    • Valve Stem Seals: Worn or hardened valve stem seals can allow oil to seep into the combustion chambers, especially during deceleration.
    • Turbocharger Issues (if applicable): While your 2.5i is naturally aspirated, for turbocharged models, a failing turbo can also cause oil consumption.
    • External Leaks: Though you mentioned no visible leaks, sometimes minor leaks can evaporate before hitting the ground.

  2. When to See a Shop:

    • 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/fill cap, and having you return after a specified mileage (e.g., 1,200 miles) to measure consumption.
    • Diagnostic Scan: While not directly for oil consumption, excessive burning oil can eventually trigger a Check Engine Light with codes like P0420 (Catalyst System Efficiency Below Threshold) due to catalytic converter damage.
    • PCV System Inspection: Have the PCV valve and associated hoses inspected and replaced if necessary.
    • Compression/Leak-Down Test: These tests can help assess the health of your piston rings and valves.
    • TSBs and Recalls: Check with your dealer for any Technical Service Bulletins (TSBs) or extended warranties related to oil consumption for your specific model year and VIN. Subaru did extend warranties for some models related to this issue.

Addressing excessive oil consumption is important not only for engine longevity but also to prevent damage to emissions components like the catalytic converter, which can be very expensive to replace.

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