2011 GMC Acadia AWD with 79,200 mi. Purchased used with about 13,500 mi. Checked oil level this morning, first time checking in about 600-700 miles with a good mix of probably 70/30 percent highway to city driving in between. Oil registered on dipstick in the middle of add oil red zone, added about 1 quart of oil to get it towards the top of the "normal" zone. First time I have ever seen this much of a drop, have not added any oil since oil change and Oil Life Monitor (OLM) is at about 35% now. At most I will typically need to top off 1/2 quart between OCI and not always at that. No noticeable oil leaks in garage but have not gotten underneath with my creeper yet. I change my own oil typically when OLM gauge gets within 10% life and use AC Delco or Wix filters with Pennzoil Platinum 5w-20 and have been doing so for the past 40k miles. I know 5W-30 is spec'd but this exceeds dexos1 requirements. Any ideas?