2016 Forester 2.5i Burning Excessive Oil - Is this normal?

ClearTheCode admin answer:

Excessive oil consumption in the 2.5L naturally aspirated Boxer engines, particularly in models like your 2016 Subaru Forester, has been a well-documented issue for certain Subaru vehicles. While some oil consumption is normal for any engine, needing to add a quart or more between 5,000-mile oil changes is generally considered excessive.

Here's a breakdown of the situation:

1. Background: Earlier generations of Subaru's FB-series engines (which includes your 2.5L) were known for issues with piston rings that didn't properly seat, leading to oil bypassing into the combustion chambers. While Subaru implemented revisions, some vehicles, even in later model years, can still exhibit this trait.
2. Diagnostic Steps:
   • Oil Consumption Test: The first step is typically for a Subaru dealership to perform an official oil consumption test. This involves draining your oil, filling it to the correct level, sealing the dipstick and drain plug, and having you return after a certain mileage (e.g., 1,200 miles) to measure the consumption. This is crucial for warranty claims or extended service programs.
   • Visual Inspection: A technician will also thoroughly inspect for external leaks, though you've already checked for this.
3. Potential Causes:
   • Piston Ring Design: The primary suspected cause in many cases is the design of the piston oil control rings, which may not adequately scrape oil from the cylinder walls.
   • PCV System: A clogged or malfunctioning Positive Crankcase Ventilation (PCV) valve can also contribute to increased oil consumption.
   • Valve Stem Seals: Less common but possible, worn valve stem seals can allow oil to enter the combustion chamber.
4. TSBs/Extended Warranties: Subaru did offer an extended warranty on certain engine components (like the short block) for excessive oil consumption on specific model years, though you'd need to check if your VIN falls under any active programs. There have been TSBs related to engine software updates that attempt to mitigate consumption, but often the root cause is mechanical.

When to See a Shop: You should schedule an appointment with your Subaru dealership to initiate an official oil consumption test. Documenting your oil additions is helpful. If the test confirms excessive consumption, Subaru may offer a repair, which often involves replacing the short block (the engine block with pistons, connecting rods, and crankshaft). Address this promptly to prevent potential long-term engine damage from consistently running low on oil.