Has anyone ever heard of a "frost plug" on an XF engine? Something that, if loose, would cause engine oil to leak out? Like, all of it? If you know, where is it and what is it for?

 

I think you mean freeze plug. It is for the coolant.

A true freeze plug is an expansion plug located in the side of an engine block that is supposed to protect the block against freeze damage. Water expands when it turns to ice, and if the coolant does not have enough protection it can freeze and crack the engine block. The freeze plugs (there are usually several) are supposed to pop out under such conditions to relieve the pressure on the block.

 

So...this would have nothing to do with oil leaking out of the engine, am I right? Coolant, yes, but not oil?

 

Yes..Nothing to do with Oil..only coolant (antifreeze).

 

Now, if you lost the oil pan drain plug, this would cause all of the oil to drain to the ground.