Thanks for all the infomation on what is not a cut and dried [no pun] topic...water vapor in the crankcase and water in the oil..
Couple of points and then I will withdraw from what has become an off topic discussion from the original question.
While the pH is important for any contaminate, the quantity of any contaminate is also critical and can be the controlling factor regardless of the adverse nature of the contaminate.
Engine blow-by should not be a significant source of engine oil or surface contamination...period. If blow-by is significant enough to contaminate the oil then the motor design, assemble or state of wear is sub-standard. The boxer motor should not have sufficient blow-by to contaminate the oil. And I believe that it normally doesn't.
Compression on my GSA should be 145 psi and at 125 psi it is considered "poor". Airplane motors with 76 to 60 psi are different animals and not in this mix. All motors are not created alike.
As with the amount of contaminates [re: pH] the amount of blow-by is a huge factor; so inspite of some gases or fuel escaping past the rings [rings control the blow-by on both the piston and cylinder walls] this should not be a significant source of contamination in a modern, well designed and maintain boxer motor.
So what is "significant"? Last call, get an oil analysis and quit guessing. You folks have fun...