On BITOG it seems like viscosity is personal preference. There are guys putting 5W40 in their Prius and guys like Dr. Haas putting 0W20 in a Ferrari.
Aren't engines designed to use a specific viscosity range based on clearances? I know the operating conditions will affect viscosity, but on modern water cooled cars do you really need to adapt the oil to the operating conditions? Is this an old fashioned type of thinking that's not as relevant today? Don't modern variable valve timing systems also need a specific oil viscosity?
Are there engines that don't do so well if you use an oil too thin or too thick? Or can you just run whatever you want?
Aren't engines designed to use a specific viscosity range based on clearances? I know the operating conditions will affect viscosity, but on modern water cooled cars do you really need to adapt the oil to the operating conditions? Is this an old fashioned type of thinking that's not as relevant today? Don't modern variable valve timing systems also need a specific oil viscosity?
Are there engines that don't do so well if you use an oil too thin or too thick? Or can you just run whatever you want?