Some people like having a nice car but not taking care of it. You see it all the time. I would shorten the oil change intervals for a few changes to help clear out gunk that has built up and remove any traces of the "bargain" oil that you stated is likely in there. Congratulation on the X and welcome to the club!

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2007 E70 X5 4.8i Sport Package
8x,xxx Miles
"My Precious" (Smeagol voice)