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SI B11 03 13
Engine May 2013
Technical Service
This Service Information bulletin replaces SI B11 05 84 dated March 1985.



SUBJECT
Engine Oil Consumption

MODEL
All



information
All engines normally consume a certain amount of engine oil. This is necessary in order to properly lubricate the cylinder walls, pistons, piston rings, valves and turbocharger(s), if equipped.


In addition, engines with less than 6,000 miles will generally consume additional engine oil because the internal engine components are not fully seated (break-in). Therefore, engine oil consumption complaints received prior to 6,000 miles cannot be considered.



Once a new or remanufactured engine has accumulated 6,000 miles, oil consumption can be considered if there is a drastic change in the engine oil consumption rate (e.g., the engine oil consumption rate triples) under similar driving conditions.



Engines equipped with a turbocharger(s) will consume more engine oil than normally aspirated engines (non-turbocharged). The additional oil that is consumed in a turbocharged engine is mainly due to the turbocharger lubrication requirements. Some of the engine oil normally migrates past the turbocharger turbine bearing seals and will enter the intake tract of the engine. All turbocharged engines also require a complex crankcase ventilation system. The crankcase ventilation system needs to maintain a small vacuum on the crankcase and not allow the crankcase to be pressurized.



Pressurizing the engine crankcase can lead to external engine oil leaks and increased engine oil consumption via the piston rings and valve seals. When the load and the boost level of a turbocharged engine is varied, the path of the crankcase pressure is changed. During the crankcase ventilation path transition, a small amount of engine oil will pass through the crankcase ventilation system and is additionally consumed. The additional engine oil consumption of a turbocharged engine, as compared to a normally aspirated engine, is normal and not a defect.



oil consumption specification
All BMW engines (excluding Motorsport) can consume up to 1 quart of engine oil per 750 miles at any time.


Due to the increased engine power, all Motorsport engines can consume up to 2.5 quarts of engine oil per 1,000 miles at any time.



diagnostic hints
When an oil consumption complaint is received, it may be possible to correct it without performing extensive engine repairs. Check the following frequent causes of excessive oil consumption prior to undertaking any engine consumption analysis or repairs. Submit a PuMA case for assistance.


Proper Maintenance



Has the vehicle received proper maintenance? Certain external conditions (mainly city driving style and/or high engine loads; poor fuel quality; and extreme ambient temperatures), combined with excessively long oil service intervals, may accelerate engine oil degradation, which may cause premature wear of the engine components. Continuous city driving (stop-and-go traffic); fuels with high olefin content; sulfur and certain aromatic fractions; and very high ambient temperatures are the most influential factors causing premature oil aging and consecutive engine mechanical deterioration.



External Leakage



The engine should be leak-free before starting any engine oil consumption analysis.



Overfilling



If the oil level is too high, oil in the crankcase will be thrown against the cylinder walls and consumed. Check the dipstick markings or electronic measurement (as equipped) to be sure of accuracy. The oil level must not be higher than the upper mark.



Engine Oil Viscosity/Quality



The use of oil with the wrong viscosity rating for operating conditions can cause high oil consumption. Check the Owner's Manual to determine the proper viscosity for prevailing conditions.



Engine Speed and Load



If vehicle operating conditions are severe, oil consumption will be higher than normal. Extreme load or continuous high engine speed will result in increased oil consumption.



Crankcase Ventilation



The crankcase ventilation systems use various different crankcase ventilation valves, depending on the engine type. Although the valves all look different, they function similarly, using a spring and diaphragm assembly to control the crankcase pressure. A properly functioning pressure control valve is designed to maintain a slight vacuum (under-pressure) in the crankcase, which assures reliable crankcase venting during all engine operating conditions. One of the results of a malfunctioning crankcase ventilation system can be increased engine oil consumption. Refer to SI B11 03 08 for measuring specifications and procedures.



Turbocharged Engines



Engines that are fitted with a turbocharger(s) will consume more engine oil than naturally aspirated engines (non-turbocharged engines). In this case, a turbocharged engine could require topping of engine oil more frequently. For vehicles with N63 and N63T engines, refer to SI B11 01 13 for additional details.