I have a 11 F-350 6.7 dually with 3:73 gears. Since new it seemed to use alot of DEF but I never kept tract of how many miles I was getting out of a tank of DEF. I remember Ford saying that the DEF would last about the same as a oil change. Well most of us seem to be in the 7500 mile range for oil changes. Well in January I changed oil, fuel filters and filled the DEF tank as I was leaving on an extended trip. On the trip I was pulling a fifth wheel trailer and 3100 miles i got the 800 mile to empty alert. That seems to be really excessive use as these were pulling highway miles. With the passive regenerations I should have never be running out of DEF at 4000 miles. I have not talked to Ford yet and Im afraid I am going to get the never had this happen before story. Anybody got any input about what could be happening to use this much DEF.. Buy the way I was possitive the tank was fulol because I used 1 full container and about 2/3 of the 2nd.

Ken

 

Heavy towing like that will increase your DEF consumption, even if its on the highway. I use a half tank (which is when I dump a jug in, 2.5 can fits and gets you back to full) a month during the summer camping(2-3 hour trips typically) dragging my fiver around. To help perhaps greater (or worsen) understanding, your regens (diesel particulate filter clean cycle) and Def fluid are two different aspects of your emission system. Diesels have two problem emission's-particulates(black soot) and NOX. Regens burn up particulates trapped by the Diesel particulate filter (DPF for short) in the exhaust. NOX is a tough one to get rid of. It's main cause is high combustion temps. Part one is EGR (exhaust gas recirculation) to add inert gases into the cylinder. Part two in the exhaust is where the DEF fluid comes in. Sent through a selective catalytic convertor (SCR for short) where the DEF is injected into the exhaust to chemically separate the NOX into nitrogen and oxygen. So under heavy sustained loads it passively can keep the DPF clean but the highish RPMs and load keep temps up, hense passive DPF cleaning, but requiring DEF usage.

 

Just and FYI. Normal driving 70 mph down the freeway empty will produce EGTs around 470° to 490°.

I hook up my 13,000 lb GN horse trailer and 70 mph on the freeway is now 800°. That is why I can drive 900 miles with out an active regen, But will use up my DEF because the SCR has been working hard the whole trip because the higher combustion temps in the cylinders produce more NOx.

The soot % and the NOx production are not directly connected. Hence Regens and DEF consumption are not directly related.

 

I have used between 17 to 20 gal of def in 27000 miles. I pull at least 5,000 pounds 4 approximately four time a month. Hope this helps

 

First 6,000 mi about 5 gal of DEF used. (I only towed our 12,000 lb 5-W about 700 mi.) The last 2,500 mi I have used 2.5 gal towing our 5-W. I try to add 2.5 gal when it indicator says it is below 1/2 full. It seems that I am useing about 1 gal per 1,000 mi. I thought I would use a little more towing than I do empty. 2,100 of the last 2,500 mi have been towing. Hope the helps. JG