How Much DEF Are You Using In Miles?

[Wayne M.]

[/QUOTE]

Big truck fleet spec won’t allow more than a few minutes of idle time. At all. Unless outdoor ambient temps are very high. At 1.25-gals/hr diesel consumption (coolant + oil temps kept above 150F), DEF consumption goes thru the roof.

Slowmover, Could you please cite your research reference?

It’s my recollection that at around 2012 the HD EPA idle shutdown took effect, curtailing any extended idle unless the truck was working or in PTO.
It’s also my understanding that SCR catalyst is ineffective below ~500F and that the DEF injector will be 0% in that condition, especially in cold start. Your statement of “DEF consumption goes through the roof” during idle time does not sit well with me.

 

[AH64ID]

It’s also my understanding that SCR catalyst is ineffective below ~500F and that the DEF injector will be 0% in that condition, especially in cold start. Your statement of “DEF consumption goes through the roof” during idle time does not sit well with me.[/QUOTE]

I will watch mine a little more and let you know what this disposable engine does

I do know that EGR is really high at idle... likely because SCR cannot be utilized.

 

[Newsa]

It’s also my understanding that SCR catalyst is ineffective below ~500F and that the DEF injector will be 0% in that condition, especially in cold start. Your statement of “DEF consumption goes through the roof” during idle time does not sit well with me.

I will watch mine a little more and let you know what this disposable engine does

I do know that EGR is really high at idle... likely because SCR cannot be utilized.[/QUOTE]

I agree. I previously had misconceptions about EGR at idle. But I was corrected here.

My wife is glad we have Diesel because in a hurricane evacuation we can get fuel.

 

[Wayne M.]

That’s correct. The trade off for less SCR is more EGR and vice versa.
I know with my Ford and Mack experience, you will not get nox conversion/ DEF injector duty cycle below a certain SCR EGT and that’s why so many have a hard time undoing the DEF related derates. The drive cycle is very defined.

 

[HarryOlson]

I’m a little late to this but here are my numbers since new:
35.75 gallons of DEF in 24,078 miles averaging 674 mpg.
Approximately 6,000 miles of above towing. Majority of miles are Hiway.

 

[OLEJOE]

I just put 4500 miles on mine towing 7k tt. Mine is about 600-650 miles per gallon of def and I didn’t keep up with the fuel. I may need to change my air filter after being in Colorado near the fires. It was hotter in SD than in Louisiana.

 

[slowmover]

Slowmover, Could you please cite your research reference?

It’s my recollection that at around 2012 the HD EPA idle shutdown took effect, curtailing any extended idle unless the truck was working or in PTO.
It’s also my understanding that SCR catalyst is ineffective below ~500F and that the DEF injector will be 0% in that condition, especially in cold start. Your statement of “DEF consumption goes through the roof” during idle time does not sit well with me.[/QUOTE]


A few hundred thousand miles worth, so to speak, of extended idle time (overnight idle).

Ratchet down the statement if you want.
Call it substantially increased demand.

 

[Newsa]

Slowmover, Could you please cite your research reference?

It’s my recollection that at around 2012 the HD EPA idle shutdown took effect, curtailing any extended idle unless the truck was working or in PTO.
It’s also my understanding that SCR catalyst is ineffective below ~500F and that the DEF injector will be 0% in that condition, especially in cold start. Your statement of “DEF consumption goes through the roof” during idle time does not sit well with me.

A few hundred thousand miles worth, so to speak, of extended idle time (overnight idle).

Ratchet down the statement if you want.
Call it substantially increased demand.[/QUOTE]


Possibly the increased DEF usage comes from more frequent active regens AFTER idling for extended periods of time. My 2013 USED to go through active regens at idle. After a few Emissions Flashes, it no longer regens at idle. The idle regens that my 2013 would do before the RTR flashes/ updates sounded like the stationary desoot that alfaOBD uses.

 

[AH64ID]

Possibly the increased DEF usage comes from more frequent active regens AFTER idling for extended periods of time. My 2013 USED to go through active regens at idle. After a few Emissions Flashes, it no longer regens at idle. The idle regens that my 2013 would do before the RTR flashes/ updates sounded like the stationary desoot that alfaOBD uses.

Regen and DEF consumption are two different emissions actions and don’t correlate to each other.

 

[Newsa]

Regen and DEF consumption are two different emissions actions and don’t correlate to each other.

Some say that NOx can be created during Regen. That was why I correlated them. I could be wrong.

 

[TFucili]

From what I have read, EGR and SCR have an inverse relationship, so when EGR flow is high, SCR is low, and EGR flow is highest at idle, so DEF use should be least at idle, especially since it needs sufficient heat at the inlet to not snowball the tip. DEF use is greater with load and throttle percentage.

 

[slowmover]

Running one of these engines at extended idle is 950-1100 rpm.

 

[AH64ID]

Extended idle using the CC button on my truck puts the intake at 19% and the EGR at 94% at 1100 rpms.

At standard idle, 750, with a cold SCR intake is at 89%(never noticed it higher at any rpm/load) and EGR at 75%. With a hot SCR is will be only slightly lower around 69%.

This is all after driving. If I just start and idle with a hot motor the EGR is lower and the DEF line pressure is lower. I didn’t let it idle more than a few minutes after a restart to see if it changed regimes.

My CTS2 doesn’t show usage rate and from what I’ve seen once it asks for DEF line pressure it won’t lower the pressure until shutdown. The line pressure won’t come up after a restart until the SCR is hot and I’ve been driving.... not sure how long I need to let it idle for SCR to come up.

 

[gsbrockman]

And yet another update.....

Through 215,762 miles, White Lightning has consumed 514.586 gallons and $1,452.33 dollars of DEF.

This equates to

• 419.29 average mpg of DEF
• $2.822 average cost per gallon
• $0.0067311 per mile
• $6.73 per 1,000 miles

20,813 gallons and $56,448.31 of #2 has been consumed.....and the DEF rate is 2.4724%. Lifetime #2 mpg is 10.36 mpg.

Another update again....for those that may actually care
284,827 miles
691.592 gallons
$1,975.99 dollars
411.84 avg mpg of DEF
$2.857 average cost per gallon
$0.0069375 cost per mile
$6.94 per 1,000 miles
27,627.4 gallons and $69,290.66 of #2 has been consumed....and the DEF rate is 2.5032%. Lifetime #2 mpg is 10.28 mpg.
All of the above DEF was purchased bulk at the pump.

 

[AH64ID]

Another update again....for those that may actually care
284,827 miles
691.592 gallons
$1,975.99 dollars
411.84 avg mpg of DEF
$2.857 average cost per gallon
$0.0069375 cost per mile
$6.94 per 1,000 miles

All of the above DEF was purchased bulk at the pump.

How many gallons of diesel are you at?


Trying to run my DEF tank down to the light, but I have some towing coming up and don’t want to risk getting too low while towing. I’m currently at 3/16 of a tank.

 

[Ltngdrvr]

How many gallons of diesel are you at?


Trying to run my DEF tank down to the light, but I have some towing coming up and don’t want to risk getting too low while towing. I’m currently at 3/16 of a tank.

When you get down to the warning light you still have 200 miles to go.
If you can't find some DEF within 200 miles then you are in a really bad place to be driving anything!
Heck, carry a jug with you if you're that worried about it.

 

[gsbrockman]

How many gallons of diesel are you at?


Trying to run my DEF tank down to the light, but I have some towing coming up and don’t want to risk getting too low while towing. I’m currently at 3/16 of a tank.

Edited my update above....thanks for catching it. I guess I got my cart in front of my hoss.....

I wouldn’t worry about running it low....you’ll get an initial message of “DEF low refill soon” or similar then......200 miles to derate, then the counter begins.

 

[AH64ID]

I don’t like filling from a jug if I don’t have to, and 200 miles won’t be enough based on where I’m towing. I’ll likely just top off at the pump before towing.


You do burn a little more DEF than I do, even when I’m towing.. thou I don’t average the weight you do. My highest average has been 2.1% (10.8 mpg over 2100 miles), but lifetime average is 1.45% and 12.8mpg.

 

[AH64ID]

I got the DEF LOW message yesterday and filled her up today. The message is supposed to come on at around 500 miles remaining, which is pretty accurate since I put 4.9 gallons into the 5.5 gallon tank.

Miles: 3461
Hours: 134
Gallons of DEF: 4.909
MPG DEF: 705
Average DEF GPH: 0.036
Gallons of Diesel: 297
MPG Diesel: 11.6
Average Diesel GPH: 2.21
% DEF:Fuel: 1.7%
Towing miles: 1051/30%

Brings my life average to 874 mpg, 0.042 GPH, and 1.67% DEF:Fuel. Lifetime 12.86 mpg diesel.

 

[AH64ID]

Couple of fill-ups combined here.

Miles: 6350
Hours: 174
Gallons of DEF: 6.876
MPG DEF: 923
Average DEF GPH: 0.039
Gallons of Diesel: 478
MPG Diesel: 13.3
Average Diesel GPH: 2.75
% DEF:Fuel: 1.4%
Towing miles: 1921/30%

Brings my life average to 883 mpg, 0.042 GPH, and 1.62% DEF:Fuel. Lifetime 12.91 mpg diesel.