The tolerances in the bearings make the difference in
oil weight. Its like ball bearings 10 weight is one size and 30 is larger and so on. the
oil companies mixed them together to create 10-30 ect... remember when their was #1 and #2 oils 10 weight and 20 weight all the same size molecules. If the tolerances are to tight to high
oil pressure and oil will not find its way in the small places.Not saying there is anything wrong with multi weight oil.Don't raise the gas prices again oil companies.