The 2020 Subaru Ascent's 2.4L turbocharged engine can develop oil leaks from the turbocharger oil supply line or its connections. This pressurized line delivers oil to the turbo bearings and uses crush washers or O-rings that can leak when compromised.
Turbo Oil Supply System
The turbocharger requires pressurized engine oil to lubricate and cool its high-speed bearings. The oil supply line, often a braided steel or rigid metal line, connects from the engine block or oil filter housing to the turbo center section. Banjo bolts with copper crush washers typically secure these connections.
Common Leak Points
Oil supply line leaks typically occur at banjo bolt connections where crush washers fail to seal, at threaded fittings that may loosen from vibration, at the line itself if cracked or damaged, and at O-ring seals on push-connect style fittings. The high oil pressure in the supply line forces oil through any weakness.
Identifying Supply Line Leaks
These leaks present as oil dripping from the turbo area, fresh oil visible on the supply line or its fittings, oil misting onto nearby components from pressurized leak, and possible oil smell from oil contacting hot turbo housing. The leak appears above typical oil leak locations due to the turbo's elevated position.
Diagnostic Process
With the engine off and cool, visually inspect the turbo oil supply line from the block to the turbo. Clean the line and fittings, then run the engine while watching for fresh oil. Note whether oil appears at connections (suggesting washer/seal failure) or along the line (suggesting line damage). Check banjo bolt torque carefully.
Repair Approach
Banjo bolt leaks require removing the bolt, replacing the copper crush washers with new ones (never reuse crush washers), and reinstalling with proper torque. Damaged lines need complete replacement. O-ring style connections need new O-rings. After repair, run the engine and verify no leaks at operating temperature and pressure. Check oil level as some may have been lost.