Couple of observations the past week or so:
1 - You really need to drive like 45 minutes on the highway to burn any significant mayo build-up off. Everything I saw after the CCV replacement was gone after that type of drive.
2 - Regardless of the 45 minute drive if you let the X5 sit in cold temperatures the build-up starts immediately. The way to prevent this appears to be to remove oil cap. Can someone design a pressure relieving oil fill cap that auto opens when the vehicle is turned off?
3 - I'm not clear what the temperature is but it appears to be as high as 45F that the may build-up happens. Could be higher. Will see as we head into summer.
4 - Have fun explaining to your co-workers in the parking lot why you always pop your hood and "look at the engine".

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Current BMW's:
2013 E70 X5 xDrive35i Premium (mine)
2014 F25 X3 xDrive28i (hers)
Past BMW's:
2001 E46 325i
2001 E46 330ci
2003 E39 525i
2006 E53 X5 3.0i
2008 E70 X5 3.0i
2014 E84 X1