Towing Def Usage

[BarryG]

Has anyone kept track of their def usage as in miles per gallon. My def usage really goes up when towing. It seems almost excessive but I haven't tracked it (starting to this week) Empty I think I get around 800 miles per gallon of def but towing seems to drop down in the 300 miles or less per gallon. I would expect it to use more for sure and all my towing is in the mountains here so again that may contribute to it as well. Just curious as to what others are seeing for comparison.

 

[leonandlisa]

My truck is mainly used for towing, only 5,000 miles so far, but it appears about 250 miles per gallon towing. Don't have enough empty miles to track that. It uses more than my Ford did for sure, but was told it get better as I get more miles.

 

[kthaxton]

I don't have any hard numbers.....because I'm too lazy to track it.....because I really don't care about my DEF usage while towing.....but I certainly use a lot when towing.

You're welcome.

 

[EHoxie]

Def usage correlates directly to fuel usage. In general you will use about 1 gal of def to 50 gallons of fuel.

 

[Berrigan]

Has anyone kept track of their def usage as in miles per gallon. My def usage really goes up when towing. It seems almost excessive but I haven't tracked it (starting to this week) Empty I think I get around 800 miles per gallon of def but towing seems to drop down in the 300 miles or less per gallon. I would expect it to use more for sure and all my towing is in the mountains here so again that may contribute to it as well. Just curious as to what others are seeing for comparison.

I could be wrong but this is my observation on DEF. Yes you use more when working the truck hard. I think DEF usage is highest when heavy throttle is used regardless of that tanks average mpg. An example is towing from 1000 foot elevation to an 8000 foot elevation and then returning to the 1000 foot elevation all on the same tank of diesel. The average mpg on that tank (because you are going down hill a lot and picking back up mpgs) on my truck isn't much different than a tank in town driving but the DEF gauge definitely moved more. I think heavy throttle really drinks up the DEF and light throttle, the ratio per gallon of diesel is less. I would like to see the logic and dosing rates explained in detail by an (in the know) type person.

 

[Cummins12V98]

24,661 miles with about 10K towing 48.789g DEF used is 505.493 mpg.

 

[kthaxton]

In summary, DEF usage is a percentage of fuel usage (2-3%??? I can't recall). If you are using more fuel (towing) you are using more DEF.

 

[BarryG]

Thanks all so far for the info. I knew it would use more when towing and expected that. And while I don't really car about how much it uses while towing I guess I am just wanting to make sure there isn't something amiss with it. As far as fuel used to def used totally makes sense. I will track for a while and see if I can get some baseline numbers. I know towing I get between 11.5 and 13.5 mpg towing vs my normal driving of 17ish mpg so towing does drop my mileage by about 30% but def usage seems to be more like double or more. However could just be the gauge and not really knowing it well enough yet. I know the top half of the tank goes a whole lot slower than the bottom half. I read an article somewhere that the first gallon plus of def can be burned/used before the gauge even starts to come off full as the float/sensor is down that low in the tank. I also found that when the gauge says E and your countdown has started and is down to 126 miles left to limp mode that I put in about 4.25 gallons before it was spilling out.

Took a quick look Cummins says def usage is about 2% of fuel consumption as Kthaxton mentioned.

 

[jhenderson]

2-3 is a range. If you use 2 when empty and 3 when towing it's still within design limits.

 

[Big E]

DEF is used to lower NOx emissions. NOx is formed at higher combustion temperatures. Working the engine hard results in higher combustion temperatures.

Therefore DEF usage will be higher when towing.

 

[Hoefler]

Towing heavy, 40' fifth wheel, I'll average 1100-1300 miles to 5 gals of DEF
Towing light, 6500 pounds, 2000-2500 miles to 5 gals of DEF
I did see 3200 miles once, but that was with a lot of bob tailing.

 

[Dan_69GTX]

Also see this thread

https://www.turbodieselregister.com/threads/256091-DEF-how-many-miles-will-a-tank-last

 

[Jared Herzog]

I started a fuelly log to track def usage. This is what i have so far and it is a mix of towing and non towing. About half and half. All my driving is in the Texas hill country. #ad
When i tow it is usually about 7-13,000 pounds. Empty i still haul around at least 500 pounds of tools in the truck.

 

[Lynx0849]

I started a fuelly log to track def usage. This is what i have so far and it is a mix of towing and non towing. About half and half. All my driving is in the Texas hill country. #ad
When i tow it is usually about 7-13,000 pounds. Empty i still haul around at least 500 pounds of tools in the truck.

Interesting app. Which app specifically is that?

 

[Jared Herzog]

Interesting app. Which app specifically is that?

Gas tracker+ for i phone by fuelly. It gives me trouble with def fill ups as it says that is too long between fill ups. It is primarily for fuel mileage. I use it on my truck also to track diesel use since day one. It has good graphs and is easy to use. #ad

 

[jorn]

When I’m towing my fiver (approx 12k lbs) I gobble the DEF. How much per mile? No idea.


When I’m empty, it’s as if I use almost no DEF at all.


When it’s low, I fill it.

 

[Cummins2014]

When I’m towing my fiver (approx 12k lbs) I gobble the DEF. How much per mile? No idea.


When I’m empty, it’s as if I use almost no DEF at all.


When it’s low, I fill it.

I hear you

 

[Kirwin]

So far 1st tank to last tank: 764 (DEF MPG), 649, 580, 1106, 854, 686, 707, 693, 728. My truck in not a daily driver, but pulls a 13K travel trailer about 75% of the mileage. Ken Irwin