I use Mobil Vactra 2. Purely because its used at work

If its good enough for £1M machines, its good enough for my lasers

.
Else, use a 3-in-1 oil. Do not use WD40, its not a lubricant. Same for grease, its a bit too heavy, you want something light that will work its way under the wipers. This should really be done a couple of drops weekly. And everytime you wipe the slideways down.
http://www.tmbelectronics.com - Electronics, tools, hobby tools, power tools, and much more!
An ex LS3020 user now playing with an LS6840PRO (60W) and an LS1290PRO (80W)