If the engine shows signs of increased oil consumption and emits blue smoke, it is imperative that the turbocharger is included in the cause analysis. Important: Oil is forced out of the housing from a turbocharger only if divergent operating conditions predominate in its environment.

-Oil is forced out of the turbine or compressor side of the turbocharger.
- Blue smoke is emitted from the exhaust system.
- Engine oil has accumulated in the intake section and charge air cooler.
- The engine experiences a power loss.
- Uncontrolled overspeeds resulting in the engine “rising” due to the engine oil accumulating in the charge air cooler, which is blown into the intake of the engine and combusted.
- The guide vanes might be coked in a VTG turbocharger.


  • If the oil return line of the turbocharger is clogged or constricted by a kink, the oil can no longer flow out of the turbocharger A possible cause for clogged oil return lines is the coking of the return line, which might be due to missing heat shields, a poorly routed return line, heat soak, inadequate oil quality, or the use of liquid sealants. As the turbocharger is still supplied with oil from the engine circuit, the oil then escapes to the turbine or compressor side.
  • If the engine is supplied with too much oil, the oil can no longer flow back out of the oil return line into the oil pan The crankshaft also splashes up the oil. This results in the oil foaming, which forms an additional barrier for the returning oil from the turbocharger If the pressure in the crankcase is too high—either because of too high blow  or due to blocked crankcase ventilation this pressure will also be transferred to the oil return

line of the turbocharger. The oil drainage from the turbocharger is thus hindered, and the oil escapes from the turbine or compressor side.

- The engine must only be filled to the specified maximum oil level.
- Only engine oils specified by the vehicle or engine manufacturer may be used.
- The oil return line must be routed exactly as in the original state. In addition, it must be ensured that all heat shields are attached.
- The oil return line and the connections to the crankcase must be checked for continuity. We generally recommend replacing the line and the connecting piece.
- The crankcase ventilation must be checked and replaced, if necessary.
- The piston and piston rings must be checked for wear and replaced, if necessary.
- A new charge air cooler and air filter should always be installed when replacing the turbocharger. In addition, an oil change including oil filter replacement must be carried out.