ENGINE OILS 3 - Partly synthetic
There is no unambiguous definition for the term partly or semi-synthetic engine oils. However, it is required when these oils are formulated that a certain part of synthetic oils and/or additives is contained in the total product.
A typical viscosity for partly synthetic oils is e.g. SAE 10W-40.
Regarding quality, partly synthetic oils have to be graded between fully synthetic and mineral products.