[GaryDoug]

I would never use any synthetic oil in a vintage engine. Those were not designed to use that oil effectively. Special designs are needed to make that work and those do not exist for the vintage designs. I speak from experience with my mistakenly using full synthetic oils in my cars. My 98TA had a big oil leak after I started using Mobile 1. I stopped that and the oil leak was reduced big time. While on a test drive, my newer 2001 TA's previous owner bragged that he started using Mobile 1 recently. I immediately said to him "I will fix that mistake". I still have yet to do that but I noticed the oil leaks have increased since I bought the car a few months ago.