Just took my oil filler cap off and noticed this white gunk
on the underside of the cap
Any one know what it is.

 

Condensation mixed with oil. It's normal. Usually it gets to be a light brown.

 

If your oil comes out looking like that you have a problem. Under the cover is normal though.

 

Thanks for the help!!!

 

Hey Fire10, I have a 2002 Dodge Ram 4.7L V-8 1500, with the same problem. Except the material is a beige mushy type material.
If you check above, you will see that i am seeking answers to the same question.
Thus far, I have been told three (3) different things.

 

If you do a search, you'll see that the consensus is, that it is condensation. It is especially pronounced during the winter months or with frequent stop and go driving where the oil doesn't get up to temp and the water doesn't evaporate out the breather. The vapor will then condense on the cooler object, which would be the filler neck. Hope this helps.