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2018 F150 Lariat Diesel 4X4 Crew Cab 5.5'
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Discussion Starter · #1 ·
Just got the 20E04 for my 2018. It has just under 19k miles on it. My def tank gets less than 3500 miles when full. Is this normal or something more going on with the EGR?
 

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Just got the 20E04 for my 2018. It has just under 19k miles on it. My def tank gets less than 3500 miles when full. Is this normal or something more going on with the EGR?
@Fraidenburg - we may want to split this topic off into a new thread, as DEF usage isn't related to EGR although both systems are emissions-related but do two (2) different things.

Quick answer: unless you are towing, your DEF usage sounds high as you should be able to get ~10K miles with the 5.5 gallon DEF tank = Mine is usually around 50% empty when topped off during my 5K oil change services.

Advice: I'd pose this same question to your Service Manager/Advisor and ask them to pull the OBD codes from your vehicle to ensure all emissions systems are working correctly.
 
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2018 F150 Lariat Diesel 4X4 Crew Cab 5.5'
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Discussion Starter · #3 ·
I was just searching different threads before I posted a new one. I was wondering if it was related to the EGR problem and the 18E02 recall with the screw coming lose into the motor. I think I read a few people were having problems with the filter getting clogged or not being able to regen. I can't remember where i seen it so I asked in that thread.
 

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My DEF usage is all over the place. I swear when I hook up a trailer it goes into permanent regen mode. It never quits and goes from 5000 miles on a tank to 1250 miles. Been this way ever since I bought it new. Stealership says there is nothing wrong. Pulling trailer from AZ to TX I filled the DEF twice.
 

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My DEF usage is all over the place. I swear when I hook up a trailer it goes into permanent regen mode. It never quits and goes from 5000 miles on a tank to 1250 miles. Been this way ever since I bought it new. Stealership says there is nothing wrong. Pulling trailer from AZ to TX I filled the DEF twice.
It's definitely not in regen mode. the DPF will clean itself when towing thanks to the higher temperatures, and it likely won't go into regen unless you max out the distance of 350 miles, then it will automatically clean out whatever's in there even if not at 100% full. DEF injection rate is related almost 100% to exhaust temperature, as NOx forms under higher heat. So the higher the EGTs, the more DEF needs to be injected to counteract the increased NOx formation. This is a good thing, because otherwise you would need way more EGR to lower cylinder temperatures. DEF is the main reason that these trucks need about 25% of the EGR volume that older emission systems required (think 6.4, 6.0, etc). In fact, at high loads your EGR may be 100% closed for optimum power, and so the reduction of NOx relies solely on the DEF injection, i.e. more of it. So It's true when they say there's nothing wrong. Usage will be even higher if it's hot outside.
 

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2018 White extended cab 6.5 foot bed FX4 Tow package Lariat
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My experience has been, that while towing you can probably expect to have to fill def for every two fuel fills. Highway and rural driving while not towing doesn’t seem to be enough of a difference to even worry about. As far as I can tell.
 

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I know this is an older thread, but I'll add my data here since it's the same topic.

I just went past 4600 miles in my 2021 Lariat, and got the warning that the DEF needs to be filled up in 500 miles. That's in mixed but mostly highway driving, but no significant towing.
 

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I know this is an older thread, but I'll add my data here since it's the same topic.

I just went past 4600 miles in my 2021 Lariat, and got the warning that the DEF needs to be filled up in 500 miles. That's in mixed but mostly highway driving, but no significant towing.
Same- my truck seems to be lucky to get 5000 miles to a tank of DEF with mixed city and highway driving, been that way since last winter. Dealerships say it's "normal".
 

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Laytunes' explanation is excellent. Basically, if your EGR is closed all the time you will use more DEF to keep the NOx under control. Personally I see that as a win. Sure you will go through more DEF but the less the EGR is open the cleaner your engine is (soot wise).

Undeleted in northern Alberta winter (-30C for as long as you can remember ) my DEF range peaked 40,000km as it cannot use it frozen. While towing in the summer I seen as low as 2,000km/ tank.
 
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