WD40 states on the tin "silicon FREE"
I would not recommend silicon grease/ oil for rubber or plastic, it has in the past had an adverse affect on some rubbers. The toilet seal inparticular, and the water connection "o" rings.
I now use a recommened oil.
I have used silicon grease through work and home for years, it is excellent for smearing over the road light connections to slow down rust etc, i find it difficult to obtain now, but it is excellent for inside the 12s/n plugs and sockets.
Does anybody have a source for silicon grease?
Searched maplin end up with a 200cc can of silicon grease/ptfe, but it will not last long, expensive.