TUBE AS 1403058 - Caterpillar

Engine Oil Leaks on the Outside of the Engine
Check for leakage at the seals at each end of the crankshaft. Look for leakage at the gasket for the engine oil pan and all lubrication system connections. Look for any engine oil that may be leaking from the crankcase breather. This can be caused by combustion gas leakage around the pistons. A dirty crankcase breather will cause high pressure in the crankcase. A dirty crankcase breather will cause the gaskets and the seals to leak. Engine Oil Leaks into the Combustion Area of the Cylinders
Engine oil that is leaking into the combustion area of the cylinders can be the cause of blue smoke. There are several possible ways for engine oil to leak into the combustion area of the cylinders:
Failed valve stem seals
Leaks between worn valve guides and valve stems
Worn components or damaged components (pistons, piston rings, or dirty return holes for the engine oil)
Leaks past the seal rings in the turbocharger shaft
Overfilling of the crankcase or the engine oil pan.
Sustained operation at light loadsExcessive consumption of engine oil can also result if engine oil with the wrong viscosity is used. Engine oil viscosity can be altered by fuel or coolant leakage into the crankcase or by increased engine temperature.