DEF Usage.
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More Turbo
Joined: Aug 2005
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DEF Usage.
I had another thread here about my DEF gauge acting funny - dropping from 1/2 to about 1/8th all at once. And when I filled it up at a truck stop it only took 4 gallons. After that the Maintenance Screen DEF Level said full with 9500 miles to empty.
I took it in for service, they did some kind of software update and when I got it back the screen still read full but the miles to empty was 7500.
I've since driven 1200 miles and the DEF gauge is still at 100%. Although on the Maintenance Screen DEF Level the miles to go is down to about 3000 miles.
Is this right? Seems to me that the first tank full went only about 2100 miles and now I'm more than half of that an show no usage.
(btw.... there are 2 DEF level displays - one is the Gauge View; the other is from a Maintenance Screen that allows you to also see the DEF level.
I took it in for service, they did some kind of software update and when I got it back the screen still read full but the miles to empty was 7500.
I've since driven 1200 miles and the DEF gauge is still at 100%. Although on the Maintenance Screen DEF Level the miles to go is down to about 3000 miles.
Is this right? Seems to me that the first tank full went only about 2100 miles and now I'm more than half of that an show no usage.
(btw.... there are 2 DEF level displays - one is the Gauge View; the other is from a Maintenance Screen that allows you to also see the DEF level.
Lead Driver
Joined: Feb 2022
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Yep. Mine still reads full but is actually 80%. It does not have a float in it like a fuel tank and I think goes by weight of fluid instead. It does measure how much is used to determine how much is left, and if you use an iDash, there are settings you can use to monitor DEF.
Lead Driver
Joined: Nov 2005
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I had another thread here about my DEF gauge acting funny - dropping from 1/2 to about 1/8th all at once. And when I filled it up at a truck stop it only took 4 gallons. After that the Maintenance Screen DEF Level said full with 9500 miles to empty.
I took it in for service, they did some kind of software update and when I got it back the screen still read full but the miles to empty was 7500.
I've since driven 1200 miles and the DEF gauge is still at 100%. Although on the Maintenance Screen DEF Level the miles to go is down to about 3000 miles.
Is this right? Seems to me that the first tank full went only about 2100 miles and now I'm more than half of that an show no usage.
(btw.... there are 2 DEF level displays - one is the Gauge View; the other is from a Maintenance Screen that allows you to also see the DEF level.
I took it in for service, they did some kind of software update and when I got it back the screen still read full but the miles to empty was 7500.
I've since driven 1200 miles and the DEF gauge is still at 100%. Although on the Maintenance Screen DEF Level the miles to go is down to about 3000 miles.
Is this right? Seems to me that the first tank full went only about 2100 miles and now I'm more than half of that an show no usage.
(btw.... there are 2 DEF level displays - one is the Gauge View; the other is from a Maintenance Screen that allows you to also see the DEF level.
Also, the gauge movement is not linear, it moves quicker at some points as it drops than at other points, it is more of a loose guide than it is a precision gauge.
These truck used to not have a gauge at all, just a warning message as the tank got close to empty.
DEF usage goes up with load just like fuel usage, DEF usage is USUALLY about 2% to 3% of fuel usage, so the miles to empty varies according to use.
So, don't look at the DEF gauge as anything other than part of the reminder system.
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More Turbo
Joined: Aug 2005
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There is about 1.5 gallons of DEF in the tank ABOVE what the gauge shows when clear full, so it will read full 100% for quite a while before the gauge starts to drop if you have completely filled it at the pump.
Also, the gauge movement is not linear, it moves quicker at some points as it drops than at other points, it is more of a loose guide than it is a precision gauge.
These truck used to not have a gauge at all, just a warning message as the tank got close to empty.
DEF usage goes up with load just like fuel usage, DEF usage is USUALLY about 2% to 3% of fuel usage, so the miles to empty varies according to use.
So, don't look at the DEF gauge as anything other than part of the reminder system.
Also, the gauge movement is not linear, it moves quicker at some points as it drops than at other points, it is more of a loose guide than it is a precision gauge.
These truck used to not have a gauge at all, just a warning message as the tank got close to empty.
DEF usage goes up with load just like fuel usage, DEF usage is USUALLY about 2% to 3% of fuel usage, so the miles to empty varies according to use.
So, don't look at the DEF gauge as anything other than part of the reminder system.
Now to continue monitoring to see if it is somewhat linear as it goes to empty.
Lead Driver
Joined: Nov 2005
Posts: 8,472
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That sounds reasonable - that I overfilled the tank and it just took a long time to start registering usage on the gauge. Today it finally got down to about 92% as indicated on my Forescan app and the dash gauges started show less than full. Thanks for info.
Now to continue monitoring to see if it is somewhat linear as it goes to empty.
Now to continue monitoring to see if it is somewhat linear as it goes to empty.
The only time filling it all the way to the top could be an issue is if the temps get down to the freezing point of the DEF, 11*, then being filled all the way to the top could cause cracking of the filler lines.
I fill mine all the way to the top every time I fill at the truck stop pumps, but then I use it very quickly so no chance of freeze damage.
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Lead Driver
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Mine is at 87% and the gauge is showing open space now instead of full. The iDash shows percentage.
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or 3.2/1000
i thought this was high!!
my truck was made without an emission sensor that “will be added when available”.
could this be causing extra usage?
Lead Driver
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Lower fuel economy means you will get higher DEF usage.
Hotshot
Joined: Jul 2013
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my def gauge has indicated 100% for the last 13000 miles.
Ive posted about this a few times.
one of the commets I get is....dont fill it until you get the blah-blah warning message...something about 50 miles warning. I counter these types of comments by saying if the def guage is always indicating full....would it ever give me the blah-blah warniing?
Ive posted about this a few times.
one of the commets I get is....dont fill it until you get the blah-blah warning message...something about 50 miles warning. I counter these types of comments by saying if the def guage is always indicating full....would it ever give me the blah-blah warniing?
Lead Driver
Joined: Nov 2005
Posts: 8,472
Likes: 4,965
my def gauge has indicated 100% for the last 13000 miles.
Ive posted about this a few times.
one of the commets I get is....dont fill it until you get the blah-blah warning message...something about 50 miles warning. I counter these types of comments by saying if the def guage is always indicating full....would it ever give me the blah-blah warniing?
Ive posted about this a few times.
one of the commets I get is....dont fill it until you get the blah-blah warning message...something about 50 miles warning. I counter these types of comments by saying if the def guage is always indicating full....would it ever give me the blah-blah warniing?
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