Originally Posted By: il_signore97
This is a strawman argument that is really not true anymore in MOST applications (yes, there will always be those few engines that can grind any oil down a grade). But in general, today's synthetic 5W30 oils are generally very robust, and shear stable. So your above statements are not entirely correct.
Not according to the UOAs posted around here... More shear-stable than in the 1980s, yes, but they still usually shear below the xW-30 limit.
Also, if an engine is not shearing an oil much, it means that its minimum oil-film thickness is large and it can tolerate thinner oil.
This is a strawman argument that is really not true anymore in MOST applications (yes, there will always be those few engines that can grind any oil down a grade). But in general, today's synthetic 5W30 oils are generally very robust, and shear stable. So your above statements are not entirely correct.
Not according to the UOAs posted around here... More shear-stable than in the 1980s, yes, but they still usually shear below the xW-30 limit.
Also, if an engine is not shearing an oil much, it means that its minimum oil-film thickness is large and it can tolerate thinner oil.