DEF Newbie Question - Gauge Level and Refill

[RustyJC]

OK, as long as I've been around here, I feel like a newbie asking this question, but this is my first DEF truck. I traded my 2011 for a 2016 this week (see signature), picked it up from the dealer where I found it in Daphne, AL and drove back to Houston. The DEF gauge was showing about 5/8 full when I took delivery, and 550 miles later it's showing just over 1/2 tank. Yesterday I was given 3 each 2.5 gallon boxes of Peak Blue DEF from my son-in-law who is moving from an F-450 to an older Freightliner FL-60 that doesn't use DEF.

So, here's my question. We're heading out on a trip towing the RV. With the gauge reading just over 1/2 tank, can I squeeze 2.5 gallons of DEF in to fill the tank before we leave? If not, about where on the gauge will the tank be 2.5 gallons low? I'm not really questioning the capacity of the DEF tank as much as the accuracy of the DEF tank gauge.

Thanks for your help.

Rusty

 

[Ram4Sam]

On both my trucks so far, when the gauge is a needle width below 1/2 tank, the 2.5 gal jugs went in with no overflow........gauge shows full.

Sam

 

[RustyJC]

Thanks, Sam. That's just the information I need.

Rusty

 

[Newsa]

On my 2013, I can put in 2.5 gallons when the needle is well above 3/4. No overflow. The needle is not linear and doesn't start moving until the tank is almost down to half.

But I don't have a 2016.

 

[SnoKing]

I get a 2.5 in when I little below 1/2 tank. Make sure the DEF has not be setting around for a long time and stored in a cool place out of the sun. Boxes have a date code. If old, it is not worth the risk. I just stop at a WM when I get below 1/2 on the gauge. Chris

 

[Larry Willard]

Should be no problem. Mine was just below 1/2 when I filled up at bulk tank in FlyingJ and it took 4.8 gal. If your not going to travel a lot I would let it be until it is down below a 1/4 so the DEF stays fresher as we head into the hot summer.
Larry

 

[Mingoglia]

This is repetitive for the most part, but I'd like to pad my post count. Rule of thumb for me is if it's at half, I put a box of 2.5 in. If it's to the point where it's on red and it complains that you're getting low, I put two boxes in. Never had spillage.

I may be able to actually contribute one thing to this thread. Since you're new to DEF, and as state it has a shelf life, I don't keep mine full except when I know I'm going to be on a road trip and/towing long distances, particularly in the summer. This way you always have fresh DEF going in. I keep mine between half and empty the whole time. So I run it until it complains it's empty, put one box in, it brings it to about half, then I don't touch it again until it complains about being empty. If you don't do this, then you could literally have 6 months between putting fresh DEF in, which IMO is too long.

Mike

 

[RustyJC]

This is repetitive for the most part, but I'd like to pad my post count. Rule of thumb for me is if it's at half, I put a box of 2.5 in. If it's to the point where it's on red and it complains that you're getting low, I put two boxes in. Never had spillage.

I may be able to actually contribute one thing to this thread. Since you're new to DEF, and as state it has a shelf life, I don't keep mine full except when I know I'm going to be on a road trip and/towing long distances, particularly in the summer. This way you always have fresh DEF going in. I keep mine between half and empty the whole time. So I run it until it complains it's empty, put one box in, it brings it to about half, then I don't touch it again until it complains about being empty. If you don't do this, then you could literally have 6 months between putting fresh DEF in, which IMO is too long.

Mike

Thanks, Mike. Since I don't know what the DEF consumption rate is going to be while towing and I'm still just above 1/2 full, I'll leave it alone until it gets close to empty. If I'm not around a truck stop, there's always a Wal-Mart or auto parts store nearby to pick some up.

Rusty

 

[Kirwin]

Rusty that DEF gauge is the most inaccurate gage on the truck (except for maybe the oil pressure that is just a calculated value above 6 PSIG). You can go a long time on the top half (over 3000 miles on my truck) and it will read just below full. Then at 4700 it will be empty. Pump DEF is widely available at most any truck stop. Don't sweat running out of it.

 

[zzollwalk]

Yes..at half tank it will take a full jug to bring the gauge back to full..you can figure that every six hundred miles will use one 2.5 gal jug..

 

[BILLUA]

Congrats on the new truck Rusty!! They really are nice. I see you went to 4x4 this time...

Enjoy!

 

[gsbrockman]

Yes..at half tank it will take a full jug to bring the gauge back to full..you can figure that every six hundred miles will use one 2.5 gal jug..

You're waaaaaaaaaaay off on that statement.....

 

[RustyJC]

Congrats on the new truck Rusty!! They really are nice. I see you went to 4x4 this time...

Enjoy!

Thanks, Bill. Actually, I found the truck online while we were having a discussion over on the Facebook 5th Wheel group about Rams and the scarcity of 385/900, Aisin, 4.10 trucks in dealer stock. The dealer was in Daphne, AL, 503 miles from the house, and it was just about like I would have ordered one except for the 4x4. Since the truck was so close on everything else, I went ahead and bought it. It actually drives better than I thought it would, and since the 2WD trucks are now solid front axles, I suspect that it really doesn't make that much difference. So, the 4x4 was just a bonus. I'm enjoying it so far - I'm hitching it up and seeing how it does with the RV this week. Since it's rated for 30K+ towing, our 19K GVWR RV probably won't even make it work.

Rusty

 

[kthaxton]

You're waaaaaaaaaaay off on that statement.....

Yeah......just a bit.

 

[zzollwalk]

I can only speak on my experience..I pull a 4 car trailer that's loaded all the time..I go from Raleigh Nc to long island 3 times a month..I'm full of def when I leave and when I get to long island im down to half and a 2.5 fills it up.

 

[SMcGrady]

I can only speak on my experience..I pull a 4 car trailer that's loaded all the time..I go from Raleigh Nc to long island 3 times a month..I'm full of def when I leave and when I get to long island im down to half and a 2.5 fills it up.

It seems reasonable to me... DEF consumption is tied to fuel consumption. When you tow heavy you will go through both much faster.

 

[zzollwalk]

I appreciate that..I didn't know that fuel burn equaled def burn..I felt that it had something to do with the weight..it all makes sense now..thanks..

 

[Newsa]

I can only speak on my experience..I pull a 4 car trailer that's loaded all the time..I go from Raleigh Nc to long island 3 times a month..I'm full of def when I leave and when I get to long island im down to half and a 2.5 fills it up.

If you are getting 6-7 mpg, that sounds about right......... if def use is actually 2-3% of fuel usage.

However, I think my DEF usage might be actually a little lower than 2%. Mine seems to use it slowly.

600 miles/6miles per gallon = 100 gallons of fuel. 100 x 0.025 (Which is 2.5%) would be 2.5 gallons.

It is a good approximation in my opinion?

I have never gotten that low of fuel mileage. But if you are towing 4 cars and some of them are sitting high, and you go through some hills. You might be using more fuel than some.

 

[SMcGrady]

^^what he said.. (if you like math and stuff...) :-laf

 

[gsbrockman]

It's really hard to gauge, with any kind of accuracy, DEF consumption, by re-filling 2.5 gallons at a time. If you're pulling a 4-car trailer, that in itself would limit the fuel retailers where you could buy fuel. I'd thought you would be buying bulk at the pump......due to DEF cost savings as well as the ease of negotiating your truck & trailer for fuel purchases.

DEF consumption is easily calculated by filling it all the way up, then re-filling at the pump, with total gallons used (just like hand-calculating fuel economy)

600/2.5= 240 MPG of DEF......that's definitely on the low side.