2015 Best DEF is 3 Gallons Distilled water to 1 Gallon DEF, I ran this ratio 4 Years and 45K miles error free. This Ratio 2014-17 will eliminate Most DEF Pump/Injector Codes and premature failure. This is Me in My 2013 Ram Cummins, I did the same procedure in My 2015 ED. ALL Retail DEF is 33% Urea 67% Deionized Water.
I challenge EPA and API after, When I tested the Conditional behavior of Ram VM 3.0 AECD were conditional, That's why 1.5 Years before the EPA filed against Fiat for CAA violation. Also the 90% DS 10% Urea resulted in 95% of Driving that ratio met CAA requirements of Near 0 NOx, My best calculations that your would need to drive 700K miles at WOT just to make a few OZ of NOx.
I run Platinum DEF. It's a synthetic and doesn't leave deposits like normal DEF. I had a clogged DEF injector on my 2015 three years ago. That's when I switched to Platinum.
Its all the same..... test it yourself..... Why waste the $. The deposits = Urea. DI or DS, actually DS IMO is superior to DI, DI is less cost to MFG. and that's why its used instead of DS. Thier are many that have been running DS for 10+ Year on CC/CTs error free into 700K+ miles.