Increased oil consumption in the engine can be contributed to wear caused by contamination of the oil with particles. It can also be due to dilution of the oil, for instance, with unburned fuel. In addition, several other causes are known. Here, you find a listing of the most common causes.

INCREASED OIL CONSUMPTION AND BLUE SMOKE FROM THE EXHAUST – OFTEN A SIGN OF ENGINE OIL IN THE COMBUSTION CHAMBERS ... AND THEREFORE OF WORN ENGINE PARTS.

WORN TURBO BEARINGS
If the bearings in the turbo charger are worn-out, oil leakage can be the result. This oil is then carried via the fresh air supply into the combustion area, where it is burned producing heavy smoke (see detailed description “Two significant types of damage”).

OIL RETURN LINE AT THE TURBO CHARGER IS BLOCKED
This can lead to a build-up of oil pressure in the turbo charger, which can again press the oil out of the bearings.

WORN INJECTION PUMP
When the injection pump is defective, oil can get into the fuel with the movement of the pump plunger – and the fuel-oil mixture burns, developing smoke and odour.

OIL LEVEL TOO HIGH
This causes the crankshaft to dip deeper into the oil bath. The result: significantly increased oil mist. When the oil is of low quality or old there is the additional risk that the oil starts foaming. This oil mist and if applicable also the oil foam can then reach the intake passage via the crankcase ventilation and is finally burned in the combustion chambers of the engine.

PISTON PROTRUSION NOT CORRECT
Due to incorrect piston protrusion, the piston can impact with the cylinder head. This causes vibrations that can also affect the injection nozzles, preventing them from closing completely. This leads to more fuel reaching the combustion chamber, which on the other hand results in dilution of the oil film and therefore to increased wear of the piston, the rings and the cylinder surface. When these components exceed a certain wear limit, oil consumption is increased significantly.

LOAD-BEARING ABILITY OF OIL TOO LOW
When oil change intervals are too long, and/or low-quality oil is used, the load-bearing ability of the oil decreases. This results in increased wear of all moving parts. Due to the reduced seal towards the crankcase, oil consumption can increase.

CYLINDER HEAD WARPAGE
When the cylinder head is fitted incorrectly, warpage of the cylinder head can result, for instance, when the tightening torque and/or sequence of the bolts are not observed. The same can happen when the old bolts are used again for refitting the cylinder head, since their tensile characteristics can change when tightened again. (Some manufacturers stipulate therefore the use of new bolts for every refitting of the cylinder head). The result: bores in the cylinder head lose their circular shape and can no longer be sealed by the rings, allowing oil to enter the combustion chamber (see detailed description “Two significant types of damage”).

WORN OR DAMAGED PISTON RINGS
If the piston rings are broken, jammed or fitted incorrectly, the seal to the crankcase becomes insufficient. The result: oil reaches the combustion chamber and is burned.

TWO SIGNIFICANT TYPES OF DAMAGE

LEAKING TURBO CHARGER
When the axial or radial bearing of the turbo charger is badly worn, the oil that lubricates and cools the bearings can get into the airstream via the connecting shaft of the vane wheels (see fig. 1). If it reaches the exhaust system, it gets directly to the outside via the exhaust system. At the fresh air side, it is blown into the combustion chambers and is combusted together with the air-fuel mixture. This results in both cases in blue smoke from the exhaust.

Fig. 1: A leaking turbo charger. (Green line: area with oil under normal operating conditions. Red line: oil leakage when bearings are worn)

WARPAGE IN THE CYLINDER
When the cylinder bolts are tightened in the wrong sequence or with the wrong torque, the cylinders can warp (see fig. 2). Even though this warpage is mostly limited to the ìm range, it can often no longer be compensated for by the piston rings. This allows the oil from the crankcase to get up into the combustion chamber, where it is finally burned – this leads also to blue smoke from the exhaust system.

Fig. 2: warpage of the cylinder.