I use Mobil 1 for my Gyrodec. And I replaced the original steel bearing with a ceramic one. 7/32 IN-C SI3N4 BALL GRADE 3 from bocabearings.com, they sell a 3 pack for around $5.
Michell Gyrodec, main bearing lube
I've had my Michell Gyrodec for a little less than ten years and have never lubed the main bearing since I did it during set up. Artech, its distributor, says it should be done every five to six years. Instructions for lubrication look very complicated and easily screwed up. Does anyone on this board have experience lubing the main bearing? How has that gone? Any cautions or suggestions based on experience?