I have a 2008 silverdao that makes oil vanish. I try to change the oil every 3k and loose 1 qt of oil. This time i went longer6k and lost 2 qts. No leake, no snoke, just looses oil. I have used full synthetic since day 1(5w30). Dealer is clueless, no suggestions from them. I am original owner so this is my baby. Any ideas?