2020 SUBARU WRX STI

Typical onset: 40,000-80,000 mi

Symptoms: Metallic knocking on cold start that quiets when warm, Low oil pressure warning, Rod knock under load or acceleration, Metal shavings in oil filter during changes

Fix: Rod bearings in the EJ257 are undersized for the power output, especially in modified cars or those driven hard. Once you hear the knock, you're looking at a full engine rebuild or short block replacement. 25-35 labor hours for proper engine-out rebuild with new bearings, ARP studs, and machining if needed. Many owners opt for the OEM short block plus upgraded bearings.

Estimated cost: $6,500-12,000

Typical onset: 50,000-90,000 mi

Symptoms: Sudden loss of power and misfires, White or blue smoke from exhaust, Check engine light with misfire codes (P0301-P0304), Compression test shows one cylinder below 100 psi

Fix: The EJ257's cast pistons crack between the ring lands—usually cylinder 4—from detonation, aggressive tuning, or bad gas. Requires full teardown, new pistons (forged aftermarket recommended), rings, and head gasket set. 30-40 hours engine-out. Many shops recommend doing all four pistons and upgrading to forged while you're in there.

Estimated cost: $7,000-13,000

Typical onset: 80,000-120,000 mi

Symptoms: Oil seepage visible on block below heads, Coolant smell after shutdown, Slight coolant consumption without visible leaks, White crusty buildup around head mating surface

Fix: EJ engines are notorious for external head gasket leaks—not the catastrophic internal failure, just weeping oil or coolant. Subaru revised gaskets multiple times but it still happens. Engine-out job recommended for proper access. 18-24 hours labor. Smart to do timing components, water pump, and valve cover gaskets while you're in there.

Estimated cost: $3,200-5,000

Typical onset: 60,000-100,000 mi

Symptoms: Small puddles of red fluid under car after parking, Burnt smell from transmission area, Low transmission fluid warning on dipstick check, Visible fluid on crossmember or exhaust

Fix: The hard lines running to the transmission cooler corrode at fittings or crack from vibration. Common on road-salt states. Replace both feed and return lines—3-4 hours labor including fluid refill and burping. Use OEM lines or quality aftermarket stainless braided.

Estimated cost: $450-800

Typical onset: 50,000-90,000 mi

Symptoms: Clunking when shifting from reverse to drive, Excessive drivetrain movement felt through shifter, Vibration at idle in gear, Visible torn rubber or separation on mount inspection

Fix: The rear transmission mount tears from the aggressive shifts and torque loads—especially in cars driven hard. The 6-speed is stout but it moves around when the mount gives up. Replace with OEM or upgraded polyurethane mount. 2-3 hours labor, need to support transmission from below.

Estimated cost: $300-550

Typical onset: 100,000+ mi

Symptoms: Stumbling under full throttle above 5000 RPM, Lean fuel trims on scan data, Hard starting when fuel tank below quarter tank, Fuel pressure drops under load

Fix: The in-tank fuel pump assembly can clog or weaken over time, especially if previous owners ran cheap gas or let tank get low frequently. Subaru calls for pump replacement as an assembly. Drop tank, replace pump and strainer. 3-4 hours labor. Not common on 2020s yet but documented on older EJs at high miles.

Estimated cost: $800-1,200