Well, i made the run from Ft Worth To Romney West Virginia and back as per my other post. 2015 with 20K miles, 3.31 gearing...

After a 20 hour drive, switching drivers of course, we made for a hotel in Morgantown West VA. After getting up and running out to the race track. we got back in to head for the local hotel in Romney. My exhaust fluid warning light came on showing i had 500 miles left and it began the count down. after running back and forth between the track and the hotel over the weekend, we ran down through Winchester Va and stopped at Walmart to pick up some DEF fluid.
Now, i had added fluid shortly before making the trip but did not top off. It did take the whole container but i hadn't checked the level but was concerned that i had to add. So i bought 2 jugs. I began pouring the first jug in and it overfilled with less than a gallon added??
The warning light continued to appear until we stopped and started a few times. i made the 1400 mile trek back to Ft Worth with no issue and the exhaust fluid OK shows when i do a system check. so, why did i get a warning with less than a gallon low?
Not a big deal but had me nervous that i was going to have limited speed once the count down hit zero and we planned( and did) to drive straight back. First and only problem i had with this truck. we had 2 dirt bikes and gear in the back, ran 75-78 mph and had mpg avgs from 18.1 down to 15.7 depending on wind and terrain. Overall avg was 17.2 between all tanks (calc mileage and total gallons used). the computer was accurate as well.
How much def should I be using anyway?
Sorry for the random thoughts, been a long weekend!

 

It was confused.

Don't add till it gets down to about 200 miles. Then do a compete fill.

If you use the ford fill spout it will stop when full and not spill a drop.

Very important to not overfill in freezing temps.

 

Good thing about Texas, dont see freezing much.
I was thinking it was confused as well. I need to track how far i can go on a half a tank of DEF...

 

I wait until half a tank warning then use fords def 2.5 gal with their filler hose never over fills 170000 miles no issue. About ever 3500 miles till half a tank warning for me.

p.s you can buy any def that meets fords requirement its just easy for me too pick up at my dealer drive by ever day only charges me 12 dollars take care

 

I would not worry about finding it on the road or filling up before traveling.


I will take a couple with me on a long towing trip but I don't fill it before leaving. I let it get down to <200 miles then fill.

 

I have the CTS monitor and buy a jug of DEF when it reads 66%. I realize it is not accurate, but if I wait too long, one jug doesn't fill enough to reset the 500 mile warning which comes long after the 66% reading. The one time that happened, I had to buy a second jug and used 2/3 of it, and since I was on the road, had to carry the rest until I used enough to top off.

 

I fill up at the Pilot truck stop pump about every 3,500 miles for around $2.79/gallon. I think I get over 1,000 miles per gallon.

 

Is that the norm, around 1000 mpg of def? seems like I may be using more than that...

 

around that if you are towing.

A complete full tank (5 gal I think) will last me 4500-5K.

 

Not that it matters , just curious why some of you guys wait till the countdown before filling? I like knowing I have a full tank especially in some of the desolated areas I drive thru you don't see a gas station or anything for a hundred miles or so some of the places don't even have diesel one advantage of having a transfer tank on the back LOL

 

I take some with me when traveling.

I feel that the system gets less confused by running it down.

 

How the system reads the DEF level, and uses that to calculate miles to empty.... is extremely basic. Topping the tank off and filling it at odd intervals can at times confuse the system.

In a nutshell there are 4 "rods" in the tank, 3 of them are the level indicators and one is the ground. The first level indicator is about the halfway mark, and then 2 more as the tank gets closer to empty. In other words, the system has no real clue as to the actual DEF level until it gets below that first rod at about the halfway point. Anything above that and it more or less thinks the tank is full.

When you fill the tank, the system resets an internal estimated miles to empty, since as I mentioned anything filling above the halfway point the system believes the tank is full. This will self adjust as the DEF level drops below each rod. So if you are towing for instance, the miles to empty will count down quicker as the system sees it's using more DEF.

Now as an example, let's say you continue to top off the tank and never let it go below the halfway rod. The miles to empty is slowly counting down, and continues to count down. The system never sees the level drop below the halfway mark, but the miles to empty continues counting. Eventually the system becomes confused and just defaults to the miles to empty countdown, and suddenly you'll get a warning saying to refill the DEF, even though the tank is full. That's just one example.

In short, the system wants to see the DEF levels drop so that it gets an accurate look. If it can't see what the DEF levels are on a regular basis, the system goes into a weird loop and requires a dealer reset. Newer versions of the diesel supplement owner's manual are very adamant about not refilling the DEF until the truck tells you to, and then fill completely (not partially).

More recent calibration updates have made it harder and harder to get the DEF system confused, but it can still happen in certain situations.

Simply following the owner's manual, and filling the DEF tank completely only when the truck tells you to, is the easiest and best way to keep from having issues. Anything else is increasing the chance of error in the system.

 

Pocket that makes absolute sense and thank you for explaining it. it's kind of funny that my dealer told me to continue what I'm doing, due to the fact that most people are having the problems you're describing at my dealership by allowing the countdown to happen and not resetting itself. When I check it every 3,000 miles like clockwork it says under half a tank warning I just buy the 2.5 gallons and there's always a little left that doesn't go in take care

 

Forgot to add possibly it's getting used to the way I'm doing it from day one at the first three thousand miles I added 2.5 gal. One other interesting thing I can add since I had the Flash update which I can't stand now goes into cleaning filter mode every 260 miles before was nearly 800 same driving conditions no heavy towing dealer says it's part of the new strategy more frequent Regens they only last 5 - 8 minutes at least in my experience ,but has not changed the exhaust fluid usage take care

 

If the new Flash reduces the Regen to 5 - 8 minutes, and only takes 1 mpg off when its doing it, that seems better than the old scheme which went off every 500 miles or less, took 20 - 25 minutes, and knocked 5 mpg off during.

Be interesting to hear from others that have gotten the flash: what do your regens look like now?