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Excessive Oil Consumption in my 2017 Forester 2.5i

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Angela R. · rep 0 · May 22, 3:14 AM · 1 replies · solved · Question

Vehicle: 2017 Subaru Forester 2.5i Premium

Hi all, I'm reaching out because I'm getting pretty frustrated with my 2017 Subaru Forester 2.5i Premium. It's got around 90,000 miles on it, and for the past year or so, it's been burning through oil like crazy. I have to add a quart every 1,500-2,000 miles, sometimes even less.

I've checked for leaks, and I don't see any obvious puddles under the car. There's no blue smoke from the exhaust that I can consistently spot, but the dipstick just keeps dropping. I'm diligent with my oil changes, using the recommended synthetic oil. Is this a common issue with these engines? What could be causing it, and what are my options?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:14 AM

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ClearTheCode admin answer:

Excessive oil consumption in certain Subaru engines, particularly the FB series (which includes your 2017 2.5i Forester), has been a known concern for some owners. While some oil consumption is normal, what you're describing sounds beyond typical.

Possible Causes:

  • Piston Rings: The most common culprit in these engines is often related to the design of the piston oil control rings, which can allow oil to bypass into the combustion chamber.
  • PCV (Positive Crankcase Ventilation) Valve: A clogged or faulty PCV valve can lead to increased crankcase pressure, forcing oil past seals or rings.
  • Valve Guide Seals: Worn or hardened valve guide seals can allow oil to seep down the valve stems into the combustion chamber.

Diagnostic Steps & When to See a Shop:

  1. Oil Consumption Test: The first step is usually 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 the actual consumption.
  2. Inspect PCV Valve: A relatively inexpensive check is to inspect and potentially replace the PCV valve. A stuck or clogged valve can contribute to oil burning.
  3. Compression/Leak-Down Test: These tests can help assess the health of your engine's piston rings and valves, indicating if there's significant internal wear.
  4. Professional Diagnosis: If the oil consumption test confirms excessive burning (Subaru's spec is generally less than 1 quart per 1,200 miles), or if you notice blue smoke from the exhaust, a loss of power, or a Check Engine Light (potentially P0420 due to catalytic converter damage from burning oil), it's imperative to consult with a Subaru specialist. They can advise on potential repairs, which might range from a top-end rebuild (piston rings, valve seals) to engine replacement in severe cases.
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