For the past several weeks when i check the oil dipstick the level has been decreasing. Now its in the add zone and i cant figure it out. I know its not leaking, but i dont smell it or see blue smoke indicating that its burning either. Wheres it going? Is this the start of something big??

 

Do a search for "plenum" ... you'll get your answer.

 

The only other option is a blown head gasket, check your coolant.