I had my dash out to replace my voltage limiter so I thought the same thing...let me lube the speedo cable. Ever since then the speedometer needle bounces. I have since heard that the old cable lube was a bit waxy to dampen the cable. Not sure what is true, but now I wonder if the old adage; 'if it aint broke don't fix it' is true.
Please post what you end up using and how it works out...I want my old smooth needle back.