Here's a copy and paste (the horror! reliable data be damned!) from Cummins:
https://www.cumminsfiltration.com/sites/default/files/MB10033.pdf
Q. Is the 32.5% urea solution critical?
A. Yes, The 32.5% urea concentration is the ideal solution as it provides the lowest freeze point. Also, SCR systems will be calibrated to the 32.5%, so that optimum NOx will be reduced during operation.
(this appears to be a good reason in and of itself)
Q. What is the freeze point of DEF?
A. A 32.5% solution of DEF will begin to crystallize and freeze at 12 deg F (-11 deg C). At 32.5%, both the urea and water will freeze at the same rate, ensuring that as it thaws, the fluid does not become diluted, or over concentrated. The freezing and thawing of DEF will not cause degradation of the product.
....and lastly,
Q. Can I make DEF myself? A. Cummins Filtration does not recommend customers make DEF themselves. DEF has strict requirements for maintaining concentration and purity of ingredients that is critical to the proper functioning and longevity of the SCR system. Cummins and other OEMs require that DEF used with their SCR systems meet all ISO22241 specifications as well as API certification requirements. It is recommended that end users purchase certified DEF and avoid blending it themselves. For more information about the quality standards, refer to ISO22241 which details specifications for DEF quality, handling, testing, transportation storage, and refilling
That said, I realize you have some of your own anecdotal results, I get that, good for you. I could understand the effort and reasoning behind finding a solution to an existing problem, my issue is.......
You seem to have a solution looking for a problem!
The very large majority of people don't have this problem, and I would say, the concentration of DEF is NOT the root cause of any of the problems you are attempting to address. The problem with anecdotal evidence is that your results could be purely coincidental.
Further, while you'd likely never get caught, I'm sure this could be construed as violating CAA requirements as "tampering with emission devices", since you are not using the system as designed.
In summary, all those reasons, combined with no evidence that DEF concentration is the ROOT CAUSE of the problem, seems to be a silly endeavor. However, you are free to do it! It's probably just best as a business owner to not talk about it too much.....and.....not come on a truck forum and promote it and imply the industry is wrong and foolish. The API guy you heckled probably didn't know the answer off the top of his head and was kind of dumbfounded with your Michael Moore style question. There's certainly no concentration conspiracy here....it sounds like they may have actually put some thought into it.
Attention: TDR Forum Junkies 
