The 2017 Forester with the 2.5L naturally-aspirated FB25 boxer is generally reliable, but shares the legacy head gasket and oil consumption issues that plagued earlier Subaru boxers, though less severe than EJ-series engines. Transmission cooler line failures and CVT concerns are the other notable weak points.
Excessive Oil Consumption / Piston Ring Failure
Occasional · high severityTypical onset: 60,000-120,000 mi
Symptoms: Burns 1+ quart every 1,000-2,000 miles, Blue smoke on cold start or hard acceleration, Check engine light P0011, P0021, P0028 (cam timing codes from oil starvation), Carbon buildup on valves and spark plugs
Fix: Subaru extended warranty covered this under certain campaigns, but outside that window it's a short-block replacement or complete engine rebuild. Piston rings lose tension, letting oil into combustion chambers. Shop time: 18-24 hours for short-block swap, 25-30 for full rebuild with machine work.
Estimated cost: $4,500-7,500
Head Gasket Seepage (External Leak)
Occasional · medium severityTypical onset: 80,000-140,000 mi
Symptoms: Oil wetness or residue at cylinder head mating surface, visible from below, Slight coolant smell but no overheating or milky oil, Slow coolant loss requiring top-offs every few months, Usually external weep, not internal combustion chamber failure like older EJ engines
Fix: FB-series head gaskets are less catastrophic than EJ, usually seep oil or coolant externally rather than mixing fluids. Still requires engine-out or partial disassembly depending on shop. Resurface heads, replace gaskets, timing components, and water pump while in there. 14-18 hours labor.
Estimated cost: $2,200-3,800
CVT Transmission Oil Cooler Line Leak
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Red ATF puddle under front of vehicle, Transmission slipping or shuddering when fluid level drops, Burning smell from hot fluid dripping onto exhaust, Check engine light or AT Oil Temp warning
Fix: Metal hardline or rubber hose connection at the transmission-mounted cooler corrodes or cracks. Subaru redesigned these lines multiple times. Replace cooler lines and top off CVT fluid; inspect cooler itself for contamination. 2-3 hours labor if just lines; 4-5 if cooler also damaged.
Estimated cost: $400-900
Rear Transmission Mount Failure
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Clunk or thud when shifting from Park to Drive/Reverse, Vibration or shudder during acceleration, Drivetrain 'rocks' excessively when engine revs, Visible rubber tearing or oil saturation on mount
Fix: The rear pitch-stopper mount absorbs torque; it's a wear item on all Subarus. Rubber degrades faster if oil-soaked from leaks above. Straightforward replacement on a lift, 1-1.5 hours. OEM or aftermarket options available.
Estimated cost: $200-350
Fuel Filter / Fuel Pump Assembly Clogging
Occasional · medium severityTypical onset: 90,000-130,000 mi
Symptoms: Hard starting, especially after sitting overnight, Hesitation or stumble under load at highway speeds, Check engine light P0171, P0172 (lean/rich codes), Fuel gauge erratic or inaccurate
Fix: In-tank filter sock and pump assembly can clog from sediment or ethanol fuel degradation. Subaru doesn't list a standalone filter replacement interval; it's part of the pump module. Drop tank, replace entire assembly. 3-4 hours labor.
Estimated cost: $600-1,000
Torque Converter Shudder (CVT)
Occasional · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Vibration or shudder around 40-50 mph during light acceleration, Feels like driving over rumble strips, Worsens when transmission is warm, May improve temporarily after fluid change
Fix: CVT clutch pack or torque converter lockup issue; often due to degraded fluid or software calibration. Subaru released several TSBs with reflash updates. Try fluid drain-and-fill (not full flush) with OEM Subaru CVT fluid first; if that doesn't resolve, valve body or torque converter replacement required. 8-12 hours for internal CVT work.
Estimated cost: $400-3,500
Solid choice for a used compact SUV if oil consumption history is clean and CVT has been maintained; walk away if seller can't show fluid service records or if it's burning oil.
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.