I'd love a bigger DEF tank...or less DEF consumption

[c3k]

First, the world being what it is, DEF is a thing and I gotta live with it.

My only other DEF experience is with a 2015 VW Passat TDi. It has a 4.5 gallon DEF tank. This lasts 10-13k miles. Once a year, when I'm doing my oil change, I top off the DEF tank. (I've only seen the "low DEF fluid" warning (comes on with 1,000 miles left) once. That's in 6 years of driving and filling the tank once a year.)

My truck seems to have a paltry DEF capacity of ~5.5 measly gallons. That's good for about 5,000 miles until empty. Of course, the FULL mark on the DEF tank does not show the first ~2,000 miles of use. This means the gauge seems full (low DEF use is the interpretation) and then it starts to register and really drops. (Each 1/8 mark is about 375 miles. Or, it uses a quarter of a tank of DEF for each tank of diesel fuel. After the DEF needle starts to move, I've got four fuel fill-ups before I'm immobilized due to a lack of DEF.

I don't care about the DEF consumption per mile. I -do- care about the need to fill the tank so often. (I don't want to let it get below 1/2 because I don't want to get close to the immobilizer nanny should I need to drive off somewhere.)

I would happily pay an exorbitant price for an aftermarket DEF tank that would hold about 12-15 gallons. Heck, as I'm typing this, I'm wondering if I could install a pair of OEM DEF tanks (so, another 11 gallons) up under the passenger side, and link them to the "real" tank with some hoses, air vent, and pump...maybe even a heater for those 12F or below kinda days.

If you've never used a long-range DEF tank, like the VW I described, you don't feel my pain.

Anyone hear of an aftermarket solution for this?

 

[NorthStar]

“Each 1/8 mark is about 375 miles. Or, it uses a quarter of a tank of DEF for each tank of diesel fuel. After the DEF needle starts to move, I've got four fuel fill-ups before I'm immobilized due to a lack of DEF.”

Help me understand. Are you certain you’re getting 1250 miles per tank of diesel? 5000 miles divided by 4 would be 1250 miles per tank. On a 33 gallon tank that would be 37 mpg.

 

[c3k]

“Each 1/8 mark is about 375 miles. Or, it uses a quarter of a tank of DEF for each tank of diesel fuel. After the DEF needle starts to move, I've got four fuel fill-ups before I'm immobilized due to a lack of DEF.”

Help me understand. Are you certain you’re getting 1250 miles per tank of diesel? 5000 miles divided by 4 would be 1250 miles per tank. On a 33 gallon tank that would be 37 mpg.

Nope. Maybe I wasn't clear. The FIRST 2,000 miles of DEF usage does not show on the DEF gauge. The tank sender does not register the top of the DEF tank. Once it shows FULL there's about 2 gallons of capacity left in the DEF tank. Those "top" 2 gallons get used (out of the total 5.5 capacity) and the gauge still shows FULL...down to about 3 gallons left.

That means that the DEF gauge only registers the bottom ~3 gallons of DEF fluid. That's about 3,000 miles of driving. So, 3,000 miles divided by the 8 hash marks on the DEF gauge means.... 3,000 / 8 = 375 miles/hash.

I get between 650 and 700 miles per 33 gallon diesel fill up. Doing more maths means... 675/33 = 20.5 mpg.

I'm actually running 23-25 mpg: I was using rough math. So, the DEF gauge is EVEN WORSE: I get LESS than 4 diesel fill ups once the DEF gauge starts to move off of FULL.

Here's what I wrote (I added the bold and underlined part so you can see what you may have missed):

My truck seems to have a paltry DEF capacity of ~5.5 measly gallons. That's good for about 5,000 miles until empty. Of course, the FULL mark on the DEF tank does not show the first ~2,000 miles of use. This means the gauge seems full (low DEF use is the interpretation) and then it starts to register and really drops. (Each 1/8 mark is about 375 miles. Or, it uses a quarter of a tank of DEF for each tank of diesel fuel. After the DEF needle starts to move, I've got four fuel fill-ups before I'm immobilized due to a lack of DEF.

 

[c3k]

From page 118 of the Owner's Manual (2021):

NOTE:
• The DEF tank on these vehicles is
designed with a large amount of full
reserve. So the level sensor will indicate
a full reading even before the
tank is completely full. To put it
another way, there’s additional
storage capacity in the tank above
the Full mark that’s not represented
in the gauge. You may not see any
movement in the reading – even after
driving up to 2,000 miles (3,219 km)
in some cases.

 

[Sascwatch]

Do you tow often? I like to think it tow quite a bit with numerous 1500+km trips per year while towing and I only fill my def up at each oil change interval which I do around 6000miles/10000km or 2-3 times per year.

I haven’t had the low def light come on once in over 60000km. I also average 1000-1200km per tank of fuel so in total 8-10 fill-ups per tank of def and it’s never fallen below 1/4 tank.

If I fill my def tank up until it is overflowing (which I do almost every time) it’ll take maybe 500-600 miles before the gauge comes off of full. I find the def tank to be the perfect size for my oci and driving habits which include probably 20-25% of its miles towing a decent sized trailer.

 

[bill-e]

I agree, I wish it had the 7+ gallon tank from the Gen 2 engine but I don't think that Ram didn't put a smaller tank in there to save money, it's likely a real estate issue.

In the winter one doesn't want to fill the tank until it overflows as Def Freezes at 12°f. Always leave space to account for this.

It would be interesting to know if the Ram Classic still has the larger tank.

 

[Conundrum]

A friend of mine with a Nissan Titan XD "deleted" it with a new exhaust and a tune. He claims the truck is awesome to run now, but I don't know if anyone would want to or has done that to a Ram EcoDiesel.

 

[bill-e]

A friend of mine with a Nissan Titan XD "deleted" it with a new exhaust and a tune. He claims the truck is awesome to run now, but I don't know if anyone would want to or has done that to a Ram EcoDiesel.

Lots have but you need to live where they don't require emission inspections.

 

[jent]

I imagine there isn't a larger DEF tank just because of the challenges of DEF degrading with temperature. Unless you're driving a ton there is probably a risk of the DEF going bad inside the tank (particularly if you refill it with a notable amount of DEF left in the tank every time).

 

[OleNavyMane]

Why not just carry an extra pack of the stuff onboard (and out of the way). That's my plan for long road trips that may take me far away from DEF availability. Save yourself from tinkering with the system and just add it on the fly.

 

[Sascwatch]

Why not just carry an extra pack of the stuff onboard (and out of the way). That's my plan for long road trips that may take me far away from DEF availability. Save yourself from tinkering with the system and just add it on the fly.

I carry an extra 2.5 gallon jug with me when towing my trailer up north. It’s a 3000km+ round trip and in northern Ontario you can’t count on any place to have it.

 

[Richard320]

I imagine there isn't a larger DEF tank just because of the challenges of DEF degrading with temperature. Unless you're driving a ton there is probably a risk of the DEF going bad inside the tank (particularly if you refill it with a notable amount of DEF left in the tank every time).

That's an excellent point!

Imagine keeping a five gallon jug of milk in the refrigerator. Each time it drops a gallon, you add a fresh gallon. It wouldn't take long before the whole thing starts to smell wrong. And while DEF doesn't spoil, it does degrade with time, and it's my understanding that if it loses potency, it uses more. So keeping the tank topped off all the time will actually cause it to use it faster!

 

[Mister 4x4]

Considering that DEF is 'essentially' purified water and pee, maybe this problem works itself out during the long drive with a couple of Super Big Gulps and a big bottle of distilled water?

 

[c3k]

Stopping and filling is a solution. Not a great solution...but a solution.

The analogy would be to just have the dealer go with a hypothetical 15 gallon fuel tank, and just carry a jerry can or three. (Yeah, I know: not a good analogy and a bit of a strawman. Take in the same tongue-in-cheek manner in which I'm posting it. )

The temp isn't that big a deal. My VW, explained above, keeps the SAME horse **** for a YEAR. No change in consumption in the almost 6 years I've owned it. I can't imagine that the Ram tank is more susceptible to Urea breakdown than the VW plastic. And, that VW gets fresh DEF in the early spring and we have a LOT of days when the temp is above 100F, and many more days in which the ROAD TEMP is way above 100F.

My Ram tank sits a bit higher over those hot spots than the VW tank.

Back to my (poor) analogy: most manufacturers size their vehicle fuel tanks for ~300 miles. ("Most": yes, there are exceptions.)

I would PREFER if Ram followed the VW design and had a DEF tank sized for ~ 1 year of driving. (Say, non-towing, highway, 12,000 miles. Or however many millions of kilometers that comes out to for our Canadian brethren. )

On a haul, as I fill with fuel, take a leak (yes, I see where I could combine a function there...), grab some food/drink, AND buy a bottle of DEF and fill it (with concomitant overflow and spillage: ask me why I bought a fuel cap)...that's a killer and just stops your momentum. May as well stop for the night.

Industry standard should be 10,000-15,000 miles. (Remember, you'll lose a bit of that because you'll have to stop to fill it before it gets too low. 1,000 is a good place for me.) So, that would be 9-14,000 miles. A 10 to 15 gallon tank would do that. (1 gallon of DEF per 1,000 driven miles is a rough estimate of usage.)

In fact, if I can source a spare tank, without the ridiculously expensive reductant injector pump, but just a heated transfer pump (12v) (heated so that 12F or below is not a problem), and mount it on the passenger side with some hoses to the existing tank...I think I could die a happy man.

 

[Sascwatch]

I don’t see why you couldn’t add an auxiliary tank somewhere with a transfer pump and plumb it to the fill tube at some point. I just don’t think it would be worth it. It’s odd I get over 1000 miles more range in def compared to you, maybe we have different sized tanks?

I’ll let mine run until the light comes on next time and see how much it takes. I can usually fit two 2.5 gallon jugs in at a time when it’s around 1/4 tank.

Tradesmen/Rebel have a 5.14 gallon tank and all other models have a 5.74 gallon tank. So it looks like your Laramie should have a larger tank, I wouldn’t think driving style has much affect on def usage. I’d say I’m 75-80% highway.

 

[J-Cooz]

My def usage is pretty good. I also average around 26-27mpg though..I do almost all highway driving. When towing it certainly chugs the DEF.

Sent from my SM-G781W using Tapatalk

 

[djevox]

Considering that DEF is 'essentially' purified water and pee, maybe this problem works itself out during the long drive with a couple of Super Big Gulps and a big bottle of distilled water?

Wait, so I can buy a few gallons of distilled water and pee in the tank after a night of hard drinking?

 

[Aseras]

Wait, so I can buy a few gallons of distilled water and pee in the tank after a night of hard drinking?

You'd be better off just filling it with distilled water. It will complain if you dilute it too much. But it complaining is better than the truck deciding to brick itself.

 

[djevox]

You'd be better off just filling it with distilled water. It will complain if you dilute it too much. But it complaining is better than the truck deciding to brick itself.

The second this things out of warranty, I’m DPF deleting it.

 

[Rebelguy2020]

First, the world being what it is, DEF is a thing and I gotta live with it.

My only other DEF experience is with a 2015 VW Passat TDi. It has a 4.5 gallon DEF tank. This lasts 10-13k miles. Once a year, when I'm doing my oil change, I top off the DEF tank. (I've only seen the "low DEF fluid" warning (comes on with 1,000 miles left) once. That's in 6 years of driving and filling the tank once a year.)

My truck seems to have a paltry DEF capacity of ~5.5 measly gallons. That's good for about 5,000 miles until empty. Of course, the FULL mark on the DEF tank does not show the first ~2,000 miles of use. This means the gauge seems full (low DEF use is the interpretation) and then it starts to register and really drops. (Each 1/8 mark is about 375 miles. Or, it uses a quarter of a tank of DEF for each tank of diesel fuel. After the DEF needle starts to move, I've got four fuel fill-ups before I'm immobilized due to a lack of DEF.

I don't care about the DEF consumption per mile. I -do- care about the need to fill the tank so often. (I don't want to let it get below 1/2 because I don't want to get close to the immobilizer nanny should I need to drive off somewhere.)

I would happily pay an exorbitant price for an aftermarket DEF tank that would hold about 12-15 gallons. Heck, as I'm typing this, I'm wondering if I could install a pair of OEM DEF tanks (so, another 11 gallons) up under the passenger side, and link them to the "real" tank with some hoses, air vent, and pump...maybe even a heater for those 12F or below kinda days.

If you've never used a long-range DEF tank, like the VW I described, you don't feel my pain.

Anyone hear of an aftermarket solution for this?

I don’t think you should use VW’s diesel as a comparable vehicle to Ram’s diesel, specially the 3rd generation diesel, the second generation diesel basically shut down the emission system while highway driving and FCA got a slap on the hand for it, VW got caught, having the emissions system basically almost off unless it was connected to an emission testing facility.
If I was to switch things around in comparison to what you are saying about the small tank of DEF, I would say, I wish my fuel tank was a lot bigger, like 10 times bigger 330 gallons, so I could fill both the DEF and the fuel tank once per year!
I keep a 1 gallon jug of DEF in the rear floor compartment under the mat, in case of emergency, I get a warning to fill the DEF, 800km or 500 miles left before empty. I am never that far away from a gas station, but having the spare gallon is good reassurance.