Conclusion: Part number 5272344 is a genuine Cummins turbocharger oil return pipe/connection, primarily used on 8.9-liter ISC/ISL EPA13 engines. To confirm with 100% certainty that it is the correct part for a specific engine, the ESN (Engine Serial Number) is required.
O-Ring Seal Cummins Engine ISC 8.3 – Engine QSC 8.3
It seals the joint between mated components, preventing fluid leaks and maintaining circuit pressure. It is installed in a circular seat between two mated components of the fuel system, where it creates a seal that prevents diesel leaks and pressure loss. It is not an external engine block gasket. Some sources refer to this family of seals as Fuel Shaft O-Rings, so the application may be associated with the shaft/fuel system circuit area.
We always recommend checking the ESN and CPL in the Cummins OEM catalog, because the same O-ring is used across different engine families, and the quantity and location may vary depending on the engine configuration.