WD in oil stands for "water displacement".
A common lubricant and household lubricant is WD-40.
The WD in WD-40 stands for water displacement and the 40 stands for the 40th attempt that it took the inventor of WD-40 to create a solution which actually works.
WD-40 is a type of water displacement spray which contains a blend of anti corrosion properties and lubricants.
WD-40 was originally developed to prevent corrosion and rust in the aerospace industry.
WD-40 also can double up as a degreaser and solvent which makes it very versatile.
While WD-40 is a lubricant, people say it's not a true lubricant because WD-40 lacks the film strength and viscosity that is necessary for heavy duty lubrication.
Using WD-40 in place of the proper lubricants required can cause increased wear and tear on moving parts over time.
The W in engine oils stand for "winter" which also indicates that the oil's viscosity or thickness at cold temperatures and most specifically at engine start up, when the engine is cold.
The lower the number before the "W", the thinner the oil is at colder temperatures, which means that the oil flows more easily and also lubricates the engine more quickly when it starts in cold weather.