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Excessive oil consumption on 2017 Forester 2.5i, no leaks

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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 constantly having to add oil to my 2017 Subaru Forester 2.5i Premium. It seems like I'm putting in a quart every 1,500-2,000 miles, which feels excessive. There are no visible leaks on my driveway or under the car, and I don't see any obvious smoke from the exhaust, though sometimes on a cold start, there might be a puff of blue.

The car has about 90,000 miles on it. I'm diligent with my oil changes, using the recommended synthetic oil. Is this normal for these engines, or is something wrong? What should I be looking for?

Thanks for any advice!

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

Excessive oil consumption without visible leaks is a known concern for some Subaru FB series engines, including those found in your 2017 Forester 2.5i. While some oil consumption is normal for any engine, a quart every 1,500-2,000 miles is generally considered high.

Common Causes & Diagnostics:

  1. Piston Rings: The most common culprit in these engines is often related to the design of the piston oil control rings, which can become clogged or lose tension over time, allowing oil to bypass into the combustion chamber. This is often exacerbated by short trips or infrequent oil changes with non-synthetic oils.
  2. 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 manifold.
  3. Valve Stem Seals: Worn valve stem seals can allow oil to leak past the valve guides and into the combustion chamber, especially noticeable as a puff of blue smoke on startup after the car has sat for a while.
  4. Turbocharger Issues (if applicable): While your 2.5i is naturally aspirated, for turbocharged models, a failing turbo can also cause significant oil consumption.

When to See a Shop:

  • Oil Consumption Test: The first step is to have a Subaru dealership or a reputable 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.
  • Regular Monitoring: Until you can get it checked, continue to monitor your oil level frequently (every 500-1,000 miles) and top it off as needed. Running the engine low on oil can cause severe and irreversible damage.
  • Engine Damage: Prolonged excessive oil consumption can lead to carbon buildup on valves and pistons, spark plug fouling, and eventually catalytic converter damage. Addressing the issue proactively is important for engine longevity.
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