Multigrade Motor

Is it better to use synthetic motor oil on a car with 100k m or "high millage" multigrade oil?

My husband and I use a synthetic motor oil in our cars. He has a 2 year old Cadillac and I have a 1994 Ford Explorer with almost 100,000 miles on it. We were told the synthetic oil was really good to use and so far, we have been pleased with the performance of both cars. Good luck with your choice.

---