As a cyclist and former projectionist, the general rule of lubrication is: If you can keep it drenched in oil, use oil, if the oil will leak out use grease and if you forget to oil of grease something and it jams or is clogged with dirt, use WD40 to clean it or unjam it before applying new oil or grease.
WD40 is a lubricant but its watered down with solvents so will not stay on whatever you need to lubricate and the solvents will destroy plastics and rubber. So its a lubricant in terms of its properties, but not its useage.