WD means "water displacer", not lubricant. Should have used a lubricant, not a water displacer. I like silicone products for the engine top, but sometimes I'll just use a general purpose grease.
WD40 is both a water displacer and a lubricant, if only a light-duty one. If the manufacturer and Wikipedia are to be believed...
From http://en.wikipedia.org/wiki/WD-40 :
WD-40 is the trademark name of a lubricant, penetrating oil and water-displacing spray.
WD-40's main ingredients, according to U.S. Material Safety Data Sheet information, are:
51% Stoddard solvent
25% liquefied petroleum gas (presumably as a propellant; carbon dioxide is now used instead to reduce WD-40's considerable flammability)
15+% mineral oil (light lubricating oil)
10-% inert ingredients
From http://wd40.com/about-us/myths-legends-fun-facts/ :
Myth: WD-40 Multi-Use Product is not really a lubricant.
Fact:
While the “W-D” in WD-40 stands for Water Displacement, WD-40 Multi-Use Product is a unique, special blend of lubricants. The product’s formulation also contains anti-corrosion agents and ingredients for penetration, water displacement and soil removal.