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Was driving to work this morning and scrolled through my information pages on the dash real quick at a stop light and noticed my DEF went from OK to 30%. Any idea how much DEF I need to now add? I can buy it in 1 gallon or 2.5 gallon jugs at the auto parts store. Can I buy 2.5 gallons and keep it on the shelf? Or am I better to get 1 gallon and buy it as needed?

Also, my dealer when I bought my truck sucked. How do I know if my truck is doing a regen? When I got my truck I was averaging 26mpg on my commute to work and now a month in I'm averaging 23mpg on the same commute. (Note: I also live in Vermont and it's cold, idk if that has any effect).
Thanks!
 

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When it gets down to 30% you can add 2.5gal no problem.

When your truck is doing a regen you have to be keen to notice it. They’re fairly seamless.

It’ll idle at about 900 instead of 700 but you won’t notice that on the highway. And when you decelerate you won’t get an instant reading of 99mpg on the readout either. If you use the 25mile avg mpg page, you could see avg as low as 17mpg or so for that 25mile span
 

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The truck holds like 5.1 gallons of def or something. I think last time I had to add it, I let it get to 11% or so then add. I added 1 full 2.5 gallon jug and got 2 gallons of another in before it started spilling out. If you do spill it on your truck, wipe it off quickly. DEF is urea, which is a fertilizer and fertilizer rusts things.

Also, if your truck normally averages say 27+ whenever you are watching either of the instant mpg screens, you will notice when you are in aregen as it will drop down to say 19-21 mpg when you're on good flat ground at say 65 to 70 mph.

Living in a cold climate will affect your mpgs. We were averaging 27+ before the winter but now we're around 25. You burn more fuel while the truck is warming up. You probably idle the truck for a while before jumping in it and taking off too. And winter diesel fuel isn't as efficient I believe. Has something to do with keeping your fuel from gelling up with what they add to it (think it's a diesel #1 mixture with your standard chisel #2)
 

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Yep, I spilled mine trying to cram 5 gal in as well. Even at 10% you cant fit 5 gal.

Fwiw, the next day I had a “service def system” check engine light and a limp mode warning. Guessing it was due to overfilling but not sure.
 

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I just joined, posted m issues on one of the other threads. I live in Ontario, Canada, got quite cold here. I had the engine code and warning my truck would only have 60 miles on before it would go into limp mode. This is the second time, but each time I now recall a burnt rubber smell, and perhaps coincidently, had to replace the "reductant fluid supply pump". IT did get to -30 deg C (-22 deg F) here for a few days on end, so likely froze the DEF fluid/pump. Cost (if not under warranty) - was told $1500 + taxes. That is twice in two months.
Working in mines here, we have pumps go down often, usually plastic impellers. Not sure what this pump looks like, but perhaps need stainless impellers? Ideas?
 

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I just joined, posted m issues on one of the other threads. I live in Ontario, Canada, got quite cold here. I had the engine code and warning my truck would only have 60 miles on before it would go into limp mode. This is the second time, but each time I now recall a burnt rubber smell, and perhaps coincidently, had to replace the "reductant fluid supply pump". IT did get to -30 deg C (-22 deg F) here for a few days on end, so likely froze the DEF fluid/pump. Cost (if not under warranty) - was told $1500 + taxes. That is twice in two months.
Working in mines here, we have pumps go down often, usually plastic impellers. Not sure what this pump looks like, but perhaps need stainless impellers? Ideas?
Hi living in Manitoba cold as **** here too. My 2.8 went in last week for froze def pump and they are changing a line also. They are not really fixing the problem for the future. When it goes off warranty then what 1500-2000$ repairs??
 

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If it’s frozen it won’t spit the piss out and then it goes in limp mode. No piss no regen ✌
I was referring to the title of this thread, not your vehicles condition. Any issue with the emissions will eventually put the truck in limp mode. The “piss” still doesn’t make regens. There is a tune out there that disables the DEF system. You could do that. GDE or green diesel engineering, although their tunes aren’t “green”
 

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Reading this makes me realize I need to see what DEF does and what a Regen does...Apparently what I 'thought' it did is very different than reality!
 

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Reading this makes me realize I need to see what DEF does and what a Regen does...Apparently what I 'thought' it did is very different than reality!
The exhaust after treatment can be broken into three main components that all handle different tasks.

This is how I understand it just by reading and laying under the truck and looking at where the sensors and injectors are

1: catalytic converter turns hydrocarbons and carbon monoxide into h2o and co2 very similar to a gasoline engine

2: selective catalyst reduction where basically def is injected into another catalytic converter (the DOC) to turn nox (and def) into n2, co2 and h2o. This is always happening. Def is consumed constantly and has nothing to do with regens.

3: diesel particulate filter catches the soot that would make black smoke and when it gets dirty, this triggers a regen. Regen adds raw fuel into the exhaust before the DOC which spikes exhaust temps up to probably 1100-1200 degrees which incinerates the soot off of the filter Grids.

Of course, it’s much more complex than this but that’s the aftertreatment 101
 
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