Adding oil between changes to your 2021 Forester is frustrating and worrying. Oil consumption has been a topic with certain Subaru engines, and understanding what's normal versus excessive helps you know when to take action.
What's Considered Normal
Subaru has stated that up to 1 quart per 1,200 miles is within specification for some engines—a threshold many owners consider too lenient. More realistic expectations:
- Normal: Minimal to no oil added between 6,000-mile changes
- Concerning: 1 quart per 3,000+ miles
- Excessive: 1 quart per 1,000-2,000 miles
- Severe: More than 1 quart per 1,000 miles
The FB25 Engine
The 2021 Forester uses the FB25 2.5L boxer engine. While more reliable than earlier EJ-series engines regarding head gaskets, some FB25 engines have exhibited oil consumption due to piston ring design characteristics.
Symptoms of Oil Consumption
- Oil level drops between services
- Low oil warning light
- Blue-gray exhaust smoke (especially on deceleration)
- Oil smell from exhaust
- Fouled spark plugs
Common Causes
- Piston ring design - Some engines have tight-clearance rings
- PCV system - Can draw oil into intake
- Valve stem seals - Allow oil past the guides
- Driving style - Short trips don't allow rings to seat properly
What You Can Do
- Track consumption precisely over several thousand miles
- Use Subaru-approved 0W-20 synthetic oil
- Avoid extended idle periods
- Take occasional longer drives for engine to reach full temperature
- Request official consumption test from Subaru
Repair Options
- PCV valve replacement: $50-$150
- Piston ring replacement: $2,500-$5,000
- Short block replacement: $4,000-$7,000
Some Foresters have received short block replacements under warranty for excessive consumption. Document everything.