DEF Usage

jacksonR · 08-15-2018, 07:29 PM

Does anyone have information about what is a reasonable usage of DEF in the Cummins engine? 2018 Isata 5 36DS with the Cummins in Dodge Chassis.

I am using about 2 gallons every 1000 miles which seems excessive.
I have not asked anyone else with the Dodge and Cummins but when I asked a Ford Diesel owner, he has driven 10,000 miles without adding any.

Thanks for any comments. I only have 5200 miles on the rig.

Whalenss · 08-15-2018, 07:44 PM

Sounds about right. I used about a 1/2 tank on a on a 2,000 + mile trip.

FCCank · 08-15-2018, 07:44 PM

I recall from documentation on my RAM Cummins that the DEF dose rate was between 1.5 and 2% , meaning DEF is dosed in at that rate as a percentage of the amount of diesel used, nothing to do with the amount of miles, but how much diesel fluid are you burning. (obviously towing something will burn more diesel) and this burned diesel needs to be treated with DEF.

When I tow and average a bit better than 10MPG, that 2% dose rate will run thru 2 gallons of DEF in 1000 miles.

I hope this helps somewhat? This dose rate is also computer controlled, so naturally there could be updates to the computer you may want to inquire for your specific engine?

jacksonR · 08-15-2018, 07:54 PM

Quote:

Originally Posted by FCCank

I recall from documentation on my RAM Cummins that the DEF dose rate was between 1.5 and 2% , meaning DEF is dosed in at that rate as a percentage of the amount of diesel used, nothing to do with the amount of miles, but how much diesel fluid are you burning. (obviously towing something will burn more diesel) and this burned diesel needs to be treated with DEF.

When I tow and average a bit better than 10MPG, that 2% dose rate will run thru 2 gallons of DEF in 1000 miles.

I hope this helps somewhat? This dose rate is also computer controlled, so naturally there could be updates to the computer you may want to inquire for your specific engine?

Thanks to both of you for the feedback.
I tow a Chevrolet 2500 crew cab and average about 9 MPG on my trips back and forth from Arizona to California. I have been towing in 6th gear and often use the exhaust brake. Just curious about the habit of using 6th gear. Any suggestions for towing?
Thanks

FCCank · 08-15-2018, 08:04 PM

I don't believe the EB has any influence on the amount of DEF used. That 2500 crew cab behind your Cummins is definitely why you're using the DEF (grin)
At 5200 miles, let the Cummins and tranny decide how best to tow in Tow-Haul mode and EB and enjoy your travels. Ultimate break-in period for Cummins is around 13,000 where you may see a tiny bit better MPG? (maybe)
I'm so much happier with my Cummins that when I was trying to travel with the Ford Triton V10 at 4000 RPM...

DR Quest · 08-15-2018, 08:08 PM

Just something to remember DEF does not last for a long time and you are better off filling when your tank is low then keeping it full. It will also freeze in temps lower than 32 degrees and needs room in the tank to expand. Unless I am on a long trip my tank is never over half full.

FOURWHL · 08-15-2018, 08:09 PM

Dont feel too bad, the 8.9L uses 1 gal per 50gal of diesel. Bigger the engine more it sucks down the DEF for sure

FCCank · 08-15-2018, 08:23 PM

Let me add that a 2% dose rate of DEF per gallon of diesel burned would mean that a 2 gallon jug of DEF would be consumed by approximately 100 gallons of diesel. Just using round-numbers here, but those 100 gallons of diesel could either be towing gallons (8MPG) or free-wheeling flying down the highway (22MPG)

Cypressloser · 08-15-2018, 08:38 PM

Quote:

Originally Posted by jacksonR

Does anyone have information about what is a reasonable usage of DEF in the Cummins engine? 2018 Isata 5 36DS with the Cummins in Dodge Chassis.

I am using about 2 gallons every 1000 miles which seems excessive.
I have not asked anyone else with the Dodge and Cummins but when I asked a Ford Diesel owner, he has driven 10,000 miles without adding any.

Thanks for any comments. I only have 5200 miles on the rig.

Yeah right, that must be one of those guys who say Ford never had an engine problem.
Anyways, your DEF usage sounds about right. I burned a lot more grossing 32,000 lbs in the Rockies with grades up to 14%, 2nd gear up and 2nd gear down with the exhaust brake holding near the red line. I'm planning a full delete within the next near.
Edit: That's towing the trailer btw. but the same cab chassis as yours.

rskeans · 08-15-2018, 08:46 PM

When traveling I carry 2 2.5 gal jugs in the storage bays. It's amazing how much def I use.

The Renegade · 08-15-2018, 08:58 PM

I do not believe the guy who drives the Ford. He is not telling you the truth. I have owned them and know better. Also I do not know this for certain but I bought DEF at the pump before and I have bought it by the 2 1/2 gallon container and there seemed to be a difference. But I will say I do think it is based on how much diesel you are burning and we all know there can be a difference there from tank to tank and where you buy from.

Good thread and good question.

Whalenss · 08-16-2018, 07:41 AM

Quote:

Originally Posted by DR Quest

Just something to remember DEF does not last for a long time and you are better off filling when your tank is low then keeping it full. It will also freeze in temps lower than 32 degrees and needs room in the tank to expand. Unless I am on a long trip my tank is never over half full.

Freezes at 12 degrees F. Good point on leaving expansion room in the tank during winter. Hadn’t thought about this. Thanks.

**bclemens** · 08-16-2018, 07:53 AM

Quote:

Originally Posted by FCCank

I recall from documentation on my RAM Cummins that the DEF dose rate was between 1.5 and 2% , meaning DEF is dosed in at that rate as a percentage of the amount of diesel used, nothing to do with the amount of miles, but how much diesel fluid are you burning. (obviously towing something will burn more diesel) and this burned diesel needs to be treated with DEF.

When I tow and average a bit better than 10MPG, that 2% dose rate will run thru 2 gallons of DEF in 1000 miles.

I hope this helps somewhat? This dose rate is also computer controlled, so naturally there could be updates to the computer you may want to inquire for your specific engine?

I think I posted this on another thread a while back....from what my Freightliner guy told me. Problem is I never remember, because we go so far in between questions....but 2% seems about right.

It becomes a hot button for 6 seconds...and then people start ignoring it again when they realize its fairly inconsequential to the whole scheme of things. Fill it when its low.

Nevermind...I found it. 3% is what we hear from Freightliner, Ram & Mercedes. Obviously that is based on driving style, temps, etc.

RV Randy · 08-16-2018, 02:54 PM

Quote:

Originally Posted by Mountieman

I do not believe the guy who drives the Ford. He is not telling you the truth.

X2, unless of course he has a 30 gallon DEF tank. I have an F350 and it doesn't use a lot, but no way he is going 10K with adding DEF.

Also, I don't believe it is a valid concern to only partially fill the DEF tank. The tanks have built in room for expansion, and they have heaters to melt the DEF when it does freeze. The engine ECU allows for a reduced amount of DEF flow when it freezes, and allows some time in this mode for the heater to melt the DEF, otherwise the engine would go into limp mode.

I believe you are better off keeping the DEF full even if you put the rig away for the winter. Just like a partially full fuel tank, the greater risk is getting condensation in the tank and diluting the DEF. If it sits for a very extended time that allows the DEF to go bad, it will do it whether the tank is full or half empty.

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