Just did 1000 miles, 830 towing. Had 500 miles to empty and filled 2.5 gallons up before leaving. Hit 500 miles to go again after 415 miles of towing. Added 2.5 more gallons and drove back 415 miles. Back down to 500 miles to empty.

Most DEF use ever, but did get a “reflash” on Friday before the trip.

2021 F350 towing a 7.5k 33.7ft travel trailer.

 

I just hit 3200 miles and the 500 miles to Empty showed up for DEF. I don’t recall what the 22’s and earlier achieve, but seems pretty reasonable to me especially with the fuel economy with 35” tires for most of that mileage.

H.O. Motor is a beast. Have driven all 3 brand new diesels. Not close in my mind at least at 4500-7000’ elevation.

 

I just did a 2000 mile trip with my Tremor HO diesel...used 4.7 gallons of DEF over the trip. Love this truck.

 

Just did some calculations on DEF usage....

Not towing: 431.8 mpg
towing (15k, 65 mph, flat land and big hills - no mountains yet); 270.4 MPG

YMMV. I was just curious.

On a side note, the 500 miles to empty can get annoying as it seems to telling me I am only getting 135.1 mpg as it comes on at about 1/2 tank.

 

DEF fluid consumption is related to how much NOX is being produce by the engine. You have a NOX in sensor and a NOX out senor. NOX is measured as it leave the engine and corrections are made to reduce it to meet EPA standards of that EPA year model. The NOX out sensor monitors the exhaust gasses to ensure the adjustments are correct. NOX is developed in the combustion chamber ( cylinders) at /above 2,500 degrees. The more the engine works with heavy loads ( lots of variables ) more NOX is developed, therefor more DEF is used. Also they use the EGR cooler, EGR valve to put more cooler exhaust gasses back into the cylinders to help control NOX by reducing in cylinder temps, then clean the rest up with DEF fluid in your SCR. Also to to the Question of controlling NOX without EGR, there is a Engine that has been developed that does not have a EGR cooler no more. Does have a EGR valve for heat management at idle and light loads only. Very low EGR percentage. They are treating NOX before DPF and after DPF. They did raise the compression ratio up to 23:1 in order to get exhaust temps higher by design. Looks very promising. So it has more 2 DEF dossers. DEF consumption will increase, motor more efficient, more reliable. The new engine is S13 class 8.

 

Greg, Educate me here. I've never seen EGT temps above 1300°. If NOx is created above 2500° Does it cool that fast just exiting the exhaust port?

The 6.7L HO engine, actually lowered the compression

On another note. Since I have a 23 coming, I paid close attention to my DEF usage last week as I hauled horses from Northern Utah to Jackson Hole. Only had two horses in trailer, So around 11,000 lbs, But it as the same wind & rolling resistance with two or four horses.

It was 590 miles round trip. I filled up before and immediately after getting home. Used 1.5 gallons of DEF My current truck is a 2020 F350 with 6.7L and 3.55 gears running 35x12.5 tires. Truck got 12.5 mpg fuel mileage. So my DEF usage was 393 mpg

 

Yes it does, that number is created under high pressures during the peak compression and load. There are again a lot of variables that affect the exhaust gas temp as well. You are correct that you do not want that high of a temp to enter the DPF or any other down stream components. That high of temp would severely damage them. SCR ideal temp for max efficiency is in the 750 degree range, how every it will function at other temp greater and lower but not as efficient. DPF regen is at a higher temp and varies as well but can range in the low as 850 to 1,100. Just as a side note I am a diesel tech going on for 42 years now as well as a corporate trainer For a OEM. I teach techs from dealers thru out the country that come to my classes. I red a lot on the forum, but usually do not commit much.

 

sorry if I didn't gather this from previous post'..... my question is= when my 23 6.7 is using def. on the fly does the fuel mileage suffer/is less?? I'm used to how my '19 worked with the regen ect... but this is def a different animal. TIA!

 

I’ve got 313 miles on the 2024. The FordPass app shows 7500 miles till DEF empty. Hard to believe that.

 

My 2013 6.7 was terrible on DEF mileage...seemed to drop to near zero after a delete was done....LOL

2022 6.7 had almost 5k miles and I didn't have a DEF light on when i traded it.

2023 6.7HO is at 1300 miles and is showing about 56% DEF, I am not a math wiz, but it is using a lot more DEF.

 

My 23 uses more def than previous years but (I’m no expert so I’m relying on others for this topic) I’ve heard it’s a good thing because the truck is using less egr if it’s using more def which the engine likes.

I’ll top off the def more frequently if it means the whole system runs better.

didn’t ford also enlarge the DPF and add a 9th injector which should help out?

Looks like they have made some upgrades to the emissions system and maybe it’ll all pay off with better running trucks

 

I am sure about more DEF usage means less EGR, the 2 are not related. The EGR is mounted on the exhaust manifold basically to recirculate the exhaust back in the intake to re-cycle the unused fuel and combust through the engine again
And, DEF is injected after the DPF to convert nitrogen oxides (NOx) in to nitrogen, water, and small amounts of carbon dioxide.
The main reason 2023+ use more DEF is to meet the newer and tougher emission standard and there is no way for the MFGs to get around it.
In the direction things are going, they may build a DEF tank 2X of the fuel tank
That reminds me, in the beginning I remember paying $5.95 for a 2.5gal jug of DEF....

 

Just don’t buy the jugs if you can help it. It’s much cheaper at the Truck Stops.
mine gets about 3000-3500 per full tank of DEF

 

Wait until you pull something heavy. It will use 1 gallon of DEF every 300 to 400 miles if it’s like my 2022. Empty they don’t use much DEF.

 

That number is subject to change in 10ft