Def

NYSUPstater

Well-known member
Will go thru my lil black book in truck where I write everything down incl DEF fill ups and mileage and report back.
 

NYSUPstater

Well-known member
Looking thru my lil black book, it seems I'm averaging around 4-5k miles on just over 4 gallons of DEF. That's a combo of towing/solo.
 

southernlady5464

Well-known member
If that works for you I’m glad, however, the diesel fuel is usually a lot higher so the miniscule amount saved on DEF is lost on 60 gallons of diesel fuel. JMTCW
That assumes you also get your diesel there. We don’t unless we are traveling and going further than one tank can go.
 

dave10a

Well-known member
Some one mentioned that the ratio is 50:1 diesel to DEF consumption. That may be correct although no link to verify. However, I suspect DEF consumption would be the same regardless of engine manufacturer. Also, I do not buy DEF at truck stop fuel lanes because I have not seen any reference that the DEF they are selling meets any type of certification. So I am willing to pay a little extra to assure that it is certified. That certification means that it uses pharmaceutical grade urea and double distilled deionized water. Also when you purchase DEF Blue or the Walmart brand assure that container is properly sealed. There have been reports that a few scum bags folks purchase the DEF empty the container and return the jug with tap water for full credit.
 

mlpeloquin

Well-known member
As long as things are well with the smog systems 5 gallons should go 7k miles or so. Last six months I pored through five gallons in less than 400 miles. Took it into the dealer and cost me $248.00 for quote "diagnostic testing", and a manual regeneration. Five gallons and 450 miles later another alert and into the dealer. Looks like the DEF heaters are open. So I was charged $248.00 for and intermittent open heater units that caused NOx bank failure warnings. The second time was on GM.

DEF is available almost anywhere, but I purchase and carry it. I was burned in the middle of nowhere and charged $28.00 for a gallon and another time $36.00 for a gallon. So you can get it, but I would not travel without it. If traveling close to home or big cities, then it is not a problem.
 

ksucats

Well-known member
Just finished a trip of 2200 miles pulling 16000+ 5th wheel. Moderate winds (for Kansas) and took a little over six gallons of DEF upon my return. In fact, the countdown notice (DEF low - 500 miles to whatever...) came on when gauge still showed about a third of the tank left. Again, was pulling fairly heavy, winds of 25 mph or so, and doing 65/66 mph in Colorado, Wyoming and Utah mountains (Hills ???) Engine running hotter going up the grades so expected more DEF usage.

Given past history going to New Mexico I topped off the DEF tank before leaving (truck stop until the pump handle wouldn't stay on, and then a little bit more).
 
Last edited:

LBR

Well-known member
FWIW, we have 7000+ miles on our 2017 F-450...driven approx 50% unhooked, 50% towing our 21.5K CY. It is averaging super close to 500 MPG of DEF.
 

ksucats

Well-known member
regarding the Ford quote above, I sure hope my DEF mpg picks up then because the first time my F450 drank DEF was a 1500 mile round trip (700 loaded miles plus local mileage unloaded in Albuquerque) and it took six gallons to fill the DEF tank. Now I admit that the truck was brand new - had just over 500 miles that I had put on it and was 'filled' by the dealer for delivery but the gauge did show full at the start. The second time is the trip we just completed. There is no way I'm going a tank of DEF to an oil change as indicated by the DIC. Now, that said, I know that pullling 16K plus 5th wheel with the front end being a huge barn door wind block, and driving 65 to 70 mph, plus the Kansas breezes, the truck is working hard. I know that the harder the truck works, the hotter the engine, the more DEF is used.

All this said, I'd like to see improved DEF to total miles improve, but as many others have stated in other posts/topics, if I can't afford the $$$ for the DEF I probably shouldn't be driving an F450 LOL. :cool:

Wishing all safe travels and fair winds.
 

Shortest Straw

Caught In A Mosh
All this said, I'd like to see improved DEF to total miles improve, but as many others have stated in other posts/topics, if I can't afford the $$$ for the DEF I probably shouldn't be driving an F450 LOL. :cool:

Wishing all safe travels and fair winds.


If def usage to total miles improved the system would not be operating correctly. It sounds like the general consensus among all brands is a tank of def per oil change. That is what we experience. I never have the dealer top me off at oil change. I monitor that and fill up at about half of the oils life cycle. Last year when I did not need to fill the def I looked for codes on my monitor and ended up needing that system replaced. Even if I had to fill the def twice during each oil change cycle I wouldn't complain about it. Def is the cheapest line item on a diesel these days except maybe washer fluid.
 

travelin2

Pennsylvania Chapter Leaders-retired
Well I’ll jump back into this conversation...SD doesn’t have a DEF gauge as the level is monitored via the Message Center. I was scrolling through the MC and saw my DEF was “less than half full”. What does that mean? Unknown until it says “500 miles to go”. So I picked up a jug at Wally World; 2 gallons topped the tank.
For that 2 gallons I drove 2115 miles with the BH in tow 865 of those miles. So simply stated, 1000+ miles/gallon of DEF. So about 3/2.5 gal boxes per oil change.


Sent from my iPhone using Tapatalk
 

travelin2

Pennsylvania Chapter Leaders-retired
I just got my replacement DEF heater delivered yesterday - and that looks to be a bundle of joy to replace.

https://www.amazon.com/gp/product/B07F313BR3/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Relocate down south & you shouldn’t need it!!!
I wonder just how cold it needs to be before it’s an issue around here?
There’s quite a bit of urea in that stuff. On your skin if reminds me of “nitan” a 30% nitrogen solution I used to apply to agricultural field crops. It never froze. Salted out and needed recirculated but...


Sent from my iPhone using Tapatalk
 

porthole

Retired
DEF freezes around 12 degrees.
The heater is to un-freeze the fluid for use.
The PCM does not run the DEF system when frozen so not an issue.

I started getting a DEF heater code in May. So like others with the same fault codes I guess the heater in my tank is ‘toast’

Not worth the effort to try and take it out and diagnose it without just replacing the unit when apart.
 
Top