Not sure why you think 5W40 is the wrong oil - quoting directly from the owners manual.
Viscosity grades for engine oils
When selecting an engine oil, ensure that
the engine oil belongs to one of the viscosity
grades SAE 0W-40, SAE 0W-30, SAE 5W-40,
and SAE 5W-30 or malfunctions or engine
damage may occur.◀
The engine oil quality is critical for the life of
the engine.
Quote:
Originally Posted by aerobod
The owners manual calls for a 0w20 or 0w30 Longlife-01 FE or Longlife-14 FE+ oil. Obviously the engine is engineered to work with these oil grades. In winter a 5xXX oil will be quite a bit more viscous than a 0wXX oil, likely leading to more cold start wear for an engine designed with tighter bearing tolerances and smaller oil passages used with 0w20 and 0w30 oils. I wouldn't expect any adverse effects to show up for at least 100,000km, but not using an oil that meets BMW specs will obviously lead to a voided warranty if the engine has an oil related failure.
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