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DEF Math

BurbMan
Explorer II
Explorer II
The owner's manual says my truck has a 5.5 gal DEF tank. I waited until I was down to 1/4 on the gauge, just above the red zone, and added a 2.5 gal box of Blue DEF from Advance Auto. Now the gauge reads FULL to the top.

So the gauge must be set to give you a long warning zone to keep you out of limp mode. This is only my 2nd time adding DEF so just getting used to all of this.

Also interesting is that the DEF I got said "Blue DEF" but the Peak brand is gone, and so is the manufacture date. No date or code of any kind on the box or the container so no way to know how old it is. With tax it was $15 for 2.5 gals, so $6/gal. Probably last time I'm buying it at Advance.
36 REPLIES 36

rhagfo
Explorer III
Explorer III
Cummins12V98 wrote:
15 RAM with gauge at 1/2 a 2.5 fits easily.


X2!
Russ & Paula the Beagle Belle.
2016 Ram Laramie 3500 Aisin DRW 4X4 Long bed.
2005 Copper Canyon 293 FWSLS, 32' GVWR 12,360#

"Visit and Enjoy Oregon State Parks"

noteven
Explorer III
Explorer III
What we learned in the class 8 world is high EGT's (power demand) result in increased NOx emission which = increased DEF use. In a working class 8 truck that was around 1-2% DEF vs fuel.

If I owned a DEF using pickup I would measure in some DEF fills at the pumps vs fuel used and soon have a rate vs fuel use vs work we are doing today factor to know when to fill the DEF tank.

If I messed up and needed some emergency like, I know all heavy truck and equipment dealers who sell current emissions engines are required by law to stock DEF - truck dealers, ag dealers, and likely yellow construction equipment now too. They are often located along main highways.

That would be the day I would exit a trip and drive around looking for a shopping plaza or China parts store to buy DEF in a cardboard box down aisle 300.

JKJavelin
Explorer III
Explorer III
BB_TX wrote:
Understanding DEF date code. Not obvious.

DEF date cide


This is why I tend to not buy Peak. WAY too cryptic date code. Why not just use a date?
JK
2018 Ram 3500 Laramie Cummins 6.7
2016 Open Range RF316RLS
Titan Disc Brakes
Trailair pinbox
Morryde AllTrek 4000 w/ wetbolt kit
Demco Autoslide
570 watts of Solar

2017-2022 555 Nights
2023- 106 Nights

naturist
Nomad
Nomad
The composition of DEF is spelled out in federal regulations. There is no allowance for any “secret sauce” and the allowed two components are among the cheapest compounds known to mankind. The only difference between brands is profit margin, packaging, and age/storage conditions (which are more a function of where you buy it). The $2 a gallon stuff at truck stops is your best bet on all counts and is plenty profitable for all involved.

Cummins12V98
Explorer III
Explorer III
15 RAM with gauge at 1/2 a 2.5 fits easily.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

Lantley
Nomad
Nomad
ksss wrote:
Lantley wrote:
BurbMan wrote:
They have it at Costco? Thanks for the heads up on that!

Lantley how do you know if you're out of DEF without a gauge?

You guess! Actually there is an idiot light that comes on and says" Low on DEF 100 miles to go until forced limp mode"
Except the mileage given is not accurate. It may come on 2 minutes later and say 50 miles to limp mode.
I learned to carry a box of DEF in the RV because I never know when I may run out!
I had to get off 95 in the very congested Fredricksville, VA area once to chase down a jug of DEF for fear I would go into limp mode. I'm still pissed about it.
A 2019 with no gauge is ridiculous. For that matter any year with no DEF gauge is a crime!



There is a DEF gauge on your 19 if you are not aware. It is on your DIC, just scroll through and check it and it will show up. It is like a RV gauge in the sense that it shows percentages below 30%. The 20's have a legit gauge that reads like a fuel gauge, much better than previous for sure.

I don't want warnings and lights. I want a gauge.
As far as scrolling down. I can scroll down and see.
DEF level OK! message.no percentages That's a far cry from a gauge.
Now if something can be reprogrammed I'm interested.
19'Duramax w/hips, 2022 Alliance Paradigm 390MP >BD3,r,22" Blackstone
r,RV760 w/BC20,Glow Steps, Enduraplas25,Pedego
BakFlip,RVLock,Prog.50A surge ,Hughes autoformer
Porta Bote 8.0 Nissan, Sailun S637

BB_TX
Nomad
Nomad
Understanding DEF date code. Not obvious.

DEF date cide

4x4ord
Explorer III
Explorer III
I have a DEF gauge on my 2017 Ford but the 2016 only told me it was OK or less than 1/2 of a tank. At less than 1/2 I could add a 2.5 gallon jug. I ran it out of DEF once just to see what would happen. It was extremely annoying because the warnings kept popping up on the dash. Eventually it got to the point that it limited my speed to 50 mph. I kept driving till the final warning indicated the vehicle was out of DEF and that upon shut off the engine would not restart. I had to add 2 jugs before the codes reset and the engine would start. Now that I know running out won't leave me stuck on the side of the road I very very seldom bother to even look at the gauge..... it seems like a tank of DEF lasts a very long time.
2023 F350 SRW Platinum short box 4x4.
B&W Companion
2008 Citation Platinum XL 34.5

ksss
Explorer
Explorer
Lantley wrote:
BurbMan wrote:
They have it at Costco? Thanks for the heads up on that!

Lantley how do you know if you're out of DEF without a gauge?

You guess! Actually there is an idiot light that comes on and says" Low on DEF 100 miles to go until forced limp mode"
Except the mileage given is not accurate. It may come on 2 minutes later and say 50 miles to limp mode.
I learned to carry a box of DEF in the RV because I never know when I may run out!
I had to get off 95 in the very congested Fredricksville, VA area once to chase down a jug of DEF for fear I would go into limp mode. I'm still pissed about it.
A 2019 with no gauge is ridiculous. For that matter any year with no DEF gauge is a crime!



There is a DEF gauge on your 19 if you are not aware. It is on your DIC, just scroll through and check it and it will show up. It is like a RV gauge in the sense that it shows percentages below 30%. The 20's have a legit gauge that reads like a fuel gauge, much better than previous for sure.
2020 Chevy 3500 CC 4X4 DRW D/A
2013 Fuzion 342
2011 RZR Desert Tan
2012 Sea Doo GTX 155
2018 Chevy 3500HD CC LB SRW 4X4 D/A
2015 Chevy Camaro ZL1

j3ff9ack
Explorer
Explorer
I think the DEF gauge on the RAM HD trucks (4th Gen) is similar to the waste tank indicators on RVs - there are sensors at preset levels and the level is approximate. Hopefully they are more reliable than the RV waste tank sensors though.
2007 Jayco JayFlight 27.5 RKS
2014 RAM 3500 SRW CC CTD 68RFE

IdaD
Explorer
Explorer
I think it's beyond dumb to not have a DEF gauge, or at least a way to check the level in the EVIC. Anytime I'm leaving for a longer trip I like to have my DEF tank topped off so I don't have to screw around with it until I get back home. A warning at 30% at the beginning of a trip is something I would have to deal with while on said trip.
2015 Cummins Ram 4wd CC/SB

ktmrfs
Explorer
Explorer
BurbMan wrote:
They have it at Costco? Thanks for the heads up on that!

Lantley how do you know if you're out of DEF without a gauge?



two ways
1) my truck gives an initial warning at 30% which even worst case is at least 1,000 miles. Then it continues to count down and give warnings. If I'm dumb enough to ignore the gauge for 1,000 miles I get what I deserve.
2) DEF usage is about 1 gallon of DEF for 100 gallons of diesel. pretty easy to keep track of in my head.
3) If I'm traveling, before I leave I can have a pretty good idea based on last fill how many miles I can go before the 30% warning comes on. If I think I will be close, easy enough to put a 2.5gallon jug in the bed.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!

Lantley
Nomad
Nomad
BurbMan wrote:
They have it at Costco? Thanks for the heads up on that!

Lantley how do you know if you're out of DEF without a gauge?

You guess! Actually there is an idiot light that comes on and says" Low on DEF 100 miles to go until forced limp mode"
Except the mileage given is not accurate. It may come on 2 minutes later and say 50 miles to limp mode.
I learned to carry a box of DEF in the RV because I never know when I may run out!
I had to get off 95 in the very congested Fredricksville, VA area once to chase down a jug of DEF for fear I would go into limp mode. I'm still pissed about it.
A 2019 with no gauge is ridiculous. For that matter any year with no DEF gauge is a crime!
19'Duramax w/hips, 2022 Alliance Paradigm 390MP >BD3,r,22" Blackstone
r,RV760 w/BC20,Glow Steps, Enduraplas25,Pedego
BakFlip,RVLock,Prog.50A surge ,Hughes autoformer
Porta Bote 8.0 Nissan, Sailun S637

rhagfo
Explorer III
Explorer III
Peak Blue DEF is changing their packaging and pushing that it is very pure, less contamination, for as much as I use I will continue to use it.
I also fill at 1/2 tank, and it goes to full, yes having a gauge is nice.
Russ & Paula the Beagle Belle.
2016 Ram Laramie 3500 Aisin DRW 4X4 Long bed.
2005 Copper Canyon 293 FWSLS, 32' GVWR 12,360#

"Visit and Enjoy Oregon State Parks"

LIKE2BUILD
Explorer
Explorer
Old-Biscuit wrote:
DEF is an aqueous urea solution made with 32.5% urea and 67.5% deionized water.

Brand shouldn't matter

Brand shouldn't matter, but I have a different experience. I had always used Peak Blue DEF but a local farm store had some off-brand DEF that was $7 for a 2.5 gallon container. I used the cheap stuff to fill up prior to a long trip and about 100 miles in I got a CEL and noticed that my DEF gauge started dropping MUCH faster than usual. At an O'Reilly's I used their scanner which showed a code for "Insufficient Catalyst". I topped off my DEF tank, but the CEL came back on and the excessive use of DEF continued for the trip.

When I got home I siphoned out the entire DEF tank and refilled with Peak Blue along with clearing the code. That was 6 years ago and I've used Peak ever since and have never had that code again.

Was it cheap DEF that was made at a bad spec? Maybe. Was it just old DEF that had been stored improperly and degraded? That's probably the more likely scenario. However, I decided that my track record with name brand Peak and the problems with the one use of the cheap stuff was enough to convince me to use the name brand and not risk problems just to save a few $$.

I may be spending more for no good reason, but I don't like taking the risks.

KJ
'14 Ram 2500|Crew Cab Long Bed|4X4|Cummins
Curt Q20 with Ram 5th Wheel Prep
2000 Crownline 205BR
1997 Ranger Comanche 461VS
'01 Polaris Virage TX PWC
'94 Polaris SLT750 PWC
3 Wonderful Sons (21, 15, & 13)
1 forgiving wife!!!