The 2021 Legacy represents Subaru's SGP platform refresh with CVTs that are generally more reliable than prior generations, but the 2.5L non-turbo still carries some engine oil consumption concerns and the platform has specific electrical gremlins that crop up earlier than expected.
Excessive Oil Consumption (2.5L H4)
Occasional · medium severityTypical onset: 40,000-80,000 mi
Symptoms: Low oil warning light between changes, Needing 1+ quarts between 6,000-mile intervals, Blue smoke on cold start, Carbon buildup on intake valves exacerbating the issue
Fix: Ranges from PCV valve replacement (1.5 hrs) if caught early to piston ring replacement requiring full engine teardown (18-22 hrs). Subaru extended warranty covered some cases through 2023, but 2021s are aging out. Short block replacement is the definitive fix for severe cases.
Estimated cost: $150-8,500
CVT Transmission Oil Cooler Line Leaks
Occasional · high severityTypical onset: 30,000-70,000 mi
Symptoms: Transmission fluid spots under vehicle near front-center, Burning smell after highway driving, CVT overheat warning on dash, Low fluid causing delayed engagement or slipping
Fix: Oil cooler lines crack at crimp points or where they pass near exhaust heat shields. Replacement involves dropping front subframe crossmember for access (3-4 hrs). OEM lines are NLA for some VINs forcing dealer special-order. Critical to address immediately—running CVT low destroys the unit.
Estimated cost: $600-1,200
EyeSight Camera/Sensor False Warnings
Common · low severitySymptoms: EyeSight disabled message with no obvious cause, Pre-collision braking false activations, Lane departure warnings constantly going off, System unavailable in clear weather
Fix: Usually windshield camera calibration drift or moisture intrusion in the camera housing. Requires STARLINK diagnostic tool for recalibration (1.5 hrs). Windshield replacement without proper OEM recalibration is a common cause. Some cases need camera module replacement if internal corrosion present.
Estimated cost: $250-1,400
Infotainment System Freezing/Black Screen
Occasional · low severitySymptoms: Touchscreen unresponsive on startup, Black screen but audio still works, Backup camera not displaying, System requires hard reset (hold power 15+ seconds) regularly
Fix: Software glitch in Harman head unit. Subaru issued TSB but many owners report it doesn't stick. Dealer reflash takes 1 hr but often recurs. Hardware replacement (3 hrs) is the permanent solution but expensive out-of-warranty. This is infotainment-only—engine still runs fine.
Estimated cost: $180-2,200
Front Lower Control Arm Bushing Failure
Occasional · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Clunking over bumps at low speed, Steering wander or pull to one side, Uneven inner tire wear, Visible bushing tear during inspection
Fix: SGP platform uses revised geometry but bushing compound degrades faster than older models in road salt environments. Requires complete lower control arm replacement—bushings aren't serviceable separately (2.5 hrs per side). Always do alignment after (add 1 hr).
Estimated cost: $650-1,100
Fuel Injector Carbon Fouling (Direct Injection)
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Rough idle when cold, Misfires under light throttle, Fuel economy drop of 2-3 mpg, P0300-series misfire codes
Fix: Direct injection with no port injection means carbon builds on intake valves and injector tips. Walnut blasting intake valves (4-5 hrs) is preventive maintenance Subaru doesn't advertise. Injector cleaning or replacement (2.5 hrs) if codes persist. This isn't a defect—it's physics—but owners aren't warned.
Estimated cost: $450-1,800
Solid daily driver if you're diligent with oil monitoring and CVT fluid changes, but budget for carbon cleaning and expect infotainment headaches—skip if you want true set-and-forget ownership.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.