More important but very hard to determine would be the percentage of synthetic/Group I in the blends. There is no standard. there are 3 possible reasons for Semi-synthetic:
2. The base oil won't meet Noack or other tests
Sadly I've seen too many on the market in the first two groups. Most of those in the third group can be found on these pages.
1. How can we find out what group a particular brand/type oil is?
2. With regards to a synthetic blend how would we find out the group of the mineral base stock that was blended with the synthetic oil?