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2019 Classic Laramie CC
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Thats odd since DEF is over 65% water
When I got the GDE tune I asked if I should continue using def fluid or if I could use distilled water. They said I should use def because the system is still active. Maybe it's because it would cause the sensors to not read the nox reduction when using water, you would have to ask GDE. I am not willing to take that chance, so I will continue to use def fluid. Maybe they have to say that to keep the epa approval...I was just telling the board what they told me. Make your own judgments.
 

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When I got the GDE tune I asked if I should continue using def fluid or if I could use distilled water. They said I should use def because the system is still active. Maybe it's because it would cause the sensors to not read the nox reduction when using water, you would have to ask GDE. I am not willing to take that chance, so I will continue to use def fluid. Maybe they have to say that to keep the epa approval...I was just telling the board what they told me. Make your own judgments.
I think the beef was you originally implied that distilled water would damage the DEF system. It will not as others have alluded too and may actually keep the injector from getting crystallization build up. But yes it makes sense that you would have to continue to use DEF with the compliant tune. The NOx levels have to meet the EPA requirements.

Apparently the pre-EPA GDE tune re-metered the DEF usage to last 10k miles (a full oil change) and disabled the quality and NOx checks. So the distilled water was pumped in and the trucks don't know the difference.
 

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I think the beef was you originally implied that distilled water would damage the DEF system. It will not as others have alluded too and may actually keep the injector from getting crystallization build up. But yes it makes sense that you would have to continue to use DEF with the compliant tune. The NOx levels have to meet the EPA requirements.

Apparently the pre-EPA GDE tune re-metered the DEF usage to last 10k miles (a full oil change) and disabled the quality and NOx checks. So the distilled water was pumped in and the trucks don't know the difference.
GDE said that using distilled water with the EPA compliant tune would damage the system, which I took to mean that the tune won't work properly with distilled water, not that it would hurt the actual components. Maybe GDE will chime in on this but again I was just posting what they told me.
 

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I run distilled water only with my pre-ban GDE tune. Post-ban compliant tunes require you to continue to use DEF or you'll get trouble codes, likely from both the DEF quality sensor and NoX sensor.
 
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The sole purpose in life of def is to create the chemical properties for the reaction across the scr to take place. The scr is there to strip NOx emissions apart. The other device that is there to lower NOx emissions is egr using distalled water or diluted def could mean using more egr would you really want that over using def? Older none complaint tuning it didnt matter but those days are going away.
 

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The sole purpose in life of def is to create the chemical properties for the reaction across the scr to take place. The scr is there to strip NOx emissions apart. The other device that is there to lower NOx emissions is egr using distalled water or diluted def could mean using more egr would you really want that over using def? Older none complaint tuning it didnt matter but those days are going away.
EGR IS TUNED OUT.
 

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I think the fact that I didn't distinguish between a compliant and non compliant tune is where the confusion started. Sorry guys!
I have about 500 miles now running the DEF/distilled water combo, no cel's , truck is running great, fuel mileage is holding at about 22-23. No more trips for a couple of weeks now.
 
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