Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
I've always used 30000 cSt on ND gauges effectively and drilled a small hole is the damper to replenish You need to exercise care of course, once a few drops of silicone has been added move the needle around and add some more until the damping effect returns.The damping effect does tend to vary from gauge to gauge slightly but what you need to see is a needle that does not drop immediately to the stop when the drive is spun.