"Oil Drain
In general, the larger the oil drain, the better. However, a -10AN is typically sufficient for proper oil drainage, but try not to have an inner diameter smaller than the drain hole in the housing as this will likely cause the oil to back up in the center housing. Speaking of oil backing up in the center housing, a gravity feed needs to be just that! The oil outlet should follow the direction of gravity +/-35° when installed in the vehicle on level ground. If a gravity feed is not possible, a scavenge pump should be used to insure that oil flows freely away from the center housing.
Avoid:
Undulations in the line or extended lengths parallel to the ground
Draining into oil pan below oil level
Dead heading into a component behind the oil pan
Area behind the oil pan (windage tray window) where oil sling occurs from crankshaft
When installing your turbocharger, insure that the turbocharger axis of rotation is parallel to the level ground within +/- 15°. This means that the oil inlet/outlet should be within 15° of being perpendicular to level ground."
Oil & Water Lines | Turbobygarrett
In general, the larger the oil drain, the better. However, a -10AN is typically sufficient for proper oil drainage, but try not to have an inner diameter smaller than the drain hole in the housing as this will likely cause the oil to back up in the center housing. Speaking of oil backing up in the center housing, a gravity feed needs to be just that! The oil outlet should follow the direction of gravity +/-35° when installed in the vehicle on level ground. If a gravity feed is not possible, a scavenge pump should be used to insure that oil flows freely away from the center housing.
Avoid:
Undulations in the line or extended lengths parallel to the ground
Draining into oil pan below oil level
Dead heading into a component behind the oil pan
Area behind the oil pan (windage tray window) where oil sling occurs from crankshaft
When installing your turbocharger, insure that the turbocharger axis of rotation is parallel to the level ground within +/- 15°. This means that the oil inlet/outlet should be within 15° of being perpendicular to level ground."
Oil & Water Lines | Turbobygarrett