I believe it has to do with how well the oil "vapourizes" (it doesn't really vapourize, it's just how well the "particles" of oil spread out to lubricate everything).
For me 15 was the lightest of what I could get my hands on (from a local hobby shop not a specialist RC shop or anything). So that's what I use. However I would jump at the chance to get lighter. (The AI silicone oil I'm told is 1.5 wt. but can only be bought in bulk (in barrels of oil not millilitres or anything like that but whole barrels ie. ~160 litres of oil in 1 barrel) for "industrial applications" or something similar).
However for me I would probably substitute White Lithium Grease and powdered graphite instead of using 60 weight silicone oil.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE
Last edited by L473ncy; August 19th, 2010 at 00:14..