for cubes of all sizes and kinds i would suggest petroleum jelly for the first 2 weeks and then take the jelly out and replace it with shock oil or silicone spray.
I use lubix on everything 4x4 and below, above htat I use crc heavy duty silicone spray, work it in ( although for the first 10 minutes it will be hard to turn, and then as it dries it will keep getting better