If you think you are installing the correct oil/grade/viscosity in your car..........think again.
Even if you select what you think is the OEM
required viscosity, you could be wrong. GM 5W-30 viscosity approval is different than SAE 5W-30 viscosity approval. The GM approval requires better low temperature pumping viscosity than SAE. And, a BMW approved 5W-30 is required to be thicker at high temperature than the SAE 10W-40 requirement. If you don’t understand the OEM proprietary and ACEA oil service rating systems, you won’t know the true viscosity of most oil products.
The whole link
Notice the mention of 5w-30 being not as thick,but even thicker than 10w-40 for BMW. So much for all those against thick oil.
Looks like a premium super synthetic of 5w-50 is just about perfect if you go by the European BMW spec.
All those skeptics making fun of 'thick oil' (5w-50 / 100% synthetic oil) should re-think that belief.