DEF Math

[BurbMan]

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.

[rhagfo]

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

X2!

[noteven]

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]

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

[naturist]

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]

15 RAM with gauge at 1/2 a 2.5 fits easily.

[Lantley]

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.

[BB_TX]

Understanding DEF date code. Not obvious.

DEF date cide

[4x4ord]

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.

[ksss]

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.

[j3ff9ack]

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.

[IdaD]

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.

[ktmrfs]

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.

[Lantley]

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!

[rhagfo]

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.

[LIKE2BUILD]

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