Pat

I use 20/50 Valvoline Syntec formulated for classic cars for the older cars. I also add the following additive. You may want to read the following. IMO extended oil changes for a light driver with synthetic oil for classics is just fine.

http://www.mossmotors.com/graphics/p...age%20Cars.pdf

Have you also considered the use of unleaded gas on internal engine parts -- valve seats, etc.? Just some food for thought. It is not just about octane.

Joe