Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

In looking at the 1977 letter from John Griffin, he states never to oil the piston or the dis-placer shaft. I knew never to oil the piston, but had not heard to never oil the dis-placer shaft. The current operating manual from PM Research for the #1 solar engine states that it's ok to oil the shaft. I wonder what has changed, or is oiling the dis-placer shaft wrong?

Mike