3 Series E30 324td (M21) TOUR
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Datum/Date:
06/2007
Update: 08/2007
Arguments concerning engine oil consumption
BMW, MINI
Situation
Customers are often uncertain when it comes to engine oil consumption. Is an engine allowed to consume oil? What
are the most important causes of engine oil consumption?
The following explanatory notes are intended as an argumentation aid. They have been compiled for all members of
staff in the dealership who have direct contact to customers.
What does the engine oil do?
The engine oil is one of the most important operating fluids in a combustion engine. Without engine oil, the engine
cannot operate correctly. The principal functions of the engine oil are:
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Lubrication
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Cooling
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Prevention of corrosion and sediment
Lubrication
The lubricating film / engine oil is subject to varying requirements. The engine oil must not have excessively high
viscosity at low temperatures to guarantee optimum lubrication even when the engine is cold (e.g. cold start). On the
other hand, the engine oil must not be too thin at high temperatures as this could cause have a negative effect on the
lubricating film, even cancelling the lubricating effect altogether.
The engine oil's most important job is to minimise friction between metallic surfaces. This is realised by a lubricating
film that forms between the surfaces of moving engine parts while the engine is running. The thin film of oil greatly
reduces friction, leading to reduced wear and less heat generation. Besides preventing pistons from seizing and
bearings from being damaged, the service life of all engine parts involved is increased and fuel consumption is
reduced.
Another function of the oil film is to seal the combustion chamber from the crankcase via the piston rings.
Cooling
The pistons reach their normal operating temperature just a few moments after the engine is started. Depending on
the ambient temperature, engine configuration and driving style, it may take a few minutes until the engine block, and
so the cylinder walls, to reach optimum operating temperature. To prevent the engine from exceeding the operating
temperature, it needs a properly functioning cooling system. The engine oil is frequently underestimated or
overlooked as an important cooling element, alongside air and coolant water. Yet the engine oil is responsible for a
large degree of cooling inside the engine. To cool the piston crowns directly, nearly all BMW engines are equipped
with oil spray jets that moisten the piston crowns with engine oil.
Prevention of corrosion and sediment
Not least, the engine oil has the job of protecting the engine against corrosion and sediment. Aggressive combustion
residue is neutralised by the lubrication oil and appropriate additives. Other combustion residue is conveyed in the oil
circuit to the oil filter where it is filtered out, or it deposits in the oil sump.
Engine oil consumption
Engine oil consumption is determined above all by the configuration of the individual construction groups and
systems. It is system characteristic that every combustion engine consumes lubricating oil. The principal causes of
this engine oil consumption are:
SI Arguments concerning engine oil consumption BMW, MINI
BMW AG - TIS
24.01.2013 23:04
Issue status (12/2007) Valid only until next DVD is issued
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