2003 Duramax running Schaeffers 15w40 Durabilty Advantage and a Wix filter for 10,530 miles. Blackstone mistakenly labeled the sample as Delo. I added 1 qt of Delo at about 6500 miles in. As stated before by others, nothing special to see. Just another boring D-Max UOA. I'll change it in another 3,000 miles as suggested. I doubt I'll spend the money on the Schaeffers this time around since my local NAPA no longer carries it. Thoughts?