DEF life span and quality considerations

[Joe Dutchstar]

An instructional video

 

[jagpot]

A lot of chatter on the web of late regarding DEF. While I don't know the details or causes I have a concern on DEF quality based on how many maintain DEF in their RV's. A lot of people like to keep their DEF tanks full, some may let it go down one indicator value such as 1 dot out of 4. Camp Freightliner pushes the rule of thumb to let it go down to two dots (half tank) prior to filling. I'm nearing the end of a long trip and I recently let my DEF get a little lower than normal, intentionally. I wanted to go lower but chickened out.

The concern many have is crystallization of the area above your DEF level. My concern and the reason I let my DEF get down to 1/2 tank prior to filling is DEF concentration, or quality. DEF has a lifespan, it does not last forever, from what I understand. If the DEF is not completely cycled out of your tank then over time you are effectively diluting your DEF by adding new to old, constantly. DEF should effectively be at a 100% concentration, in layman's terms but if you are only adding a 1/2 tank of new to 1/2 tank of old each time, what is your net effective concentration?

If I could I would drain my DEF tank annually and fill with fresh DEF. I haven't looked at what it would take to do this but my concern is growing that over time we are just reducing the quality of DEF in our RV's. My understanding from FL is you can actually run out of DEF and still travel 1,000 miles to get to a location to get DEF. I don't want to be the one to test this nor have I heard of anyone that has but the point is the system is designed to let you completely run out and not immediately de-rate you. I need to work harder on letting my DEF level get lower so I can ensure a higher concentration of quality of DEF is in my system.

The other option is to TEST your DEF. I actually own a refractometer, it's in my pegboard bay, I have yet to use it. When I get back to storage I should test it and see what it reads. I invite others to test your DEF as well and reply with your findings and share your practice of DEF management as described above and let's see what kind of statistics on DEF quality we can come up with.

DEF Refractometer for Measuring Diesel Exhaust Fluid Concentration of Diesel Engines: Amazon.com: Industrial & Scientific

DEF Refractometer for Measuring Diesel Exhaust Fluid Concentration of Diesel Engines: Amazon.com: Industrial & Scientific

www.amazon.com

Thanks Neal. I see your point. As usual you are so knowledgeable and so willing to share. Went to the link and bought it!

 

[flyboy013]

What’s the average mpg for DEF? If you could figure that out, the one could easily determine how much DEF to add at each fuel stop. If you could keep your DEF refills in sync with fuel refills, that would make life easier I think.

I did a round trip to Florida in the past two weeks. Drove 2100 miles and used roughly 12.5 gallons (5 x 2.5 gallons jugs). So I’m getting around 170 mpg.

 

[TJ&LadyDi]

The Refractometer tests the fluid concentration of urea, should be 32.5%.

Testing methods

Diesel Exhaust Fluid (DEF) Testing & Analysis - Fluid Life

Should a fault code for your diesel exhaust fluid system occur, do field and/or lab testing to detect the cause of the issue.

www.fluidlife.com

https://www.brenntag.com/media/documents/def/def-testing-methods-2016-up.pdf

Precisely! That goes to the heart of my earlier question; how does the refractometer test “quality/“. AFAIK, it simply tests the concentration of urea in the solution. Does it identify contaminants? I don’t think it does, but that’s why I asked the question. As long as the urea concentration is 32.5%, is that a “quality” check?

Inquiring minds want to know.

TJ

 

[Neal]

TJ, what is the "quality" of the gas you put in your car with respect to octane rating?

It is not about testing "quality" it is testing concentration. Our systems have DPF filters to hopefully remove contaminants (solids). The scenario I provided is mixing fresh def with "weak" def with respect to concentration. The same applies to auto gas tanks, what is the net effective octane rating if you don't fully cycle your tank? It was stated, yeah autos still run, sure, they don't require an exact octane rating. You may be putting 93 in (my Porsche) but what is the net octane rating actually in the tank? Will it run on 87, yes. My Porsche has been sitting for 6 months, do you think the octane in the tank is still 93? I don't think so. Same applies to DEF, let it sit in your tank for 2 years (being extreme), is it contaminated? No. Is it still "quality"? technically yes. Is it effective or of the proper concentration to perform its job? Will the DEF quality sensor pass based on whatever it's testing?

Choose to operate how you want. I cycle my gas for a reason (to purge the old) and will work harder to better cycle my DEF to ensure the proper concentration and effectiveness. Keep in mind some of these items attract water, i.e. ethanol! Apparently diesel has an issue with algae, which is why at times I put biocide in. Don't let your diesel run down then you are maintaining contaminants and possibly increasing them allowing them to grow, in my opinion.

There is another thread on truck stop DEF vs. boxed DEF. Many of us prefer truck stop DEF due to the turnover which probably also has a better concentration due to less shelf life. We don't know how long a box has been sitting on a delivery truck with no air conditioning, hot warehouse prior to the store shelf, and much less if it was tampered with as we've heard those stories. I will use truck stop DEF before I will resort to boxed DEF. I'm not concerned about contamination but I believe the effectiveness from the fresher DEF will be better than boxed.

How Long Does Diesel Fuel Last In Storage?

One of the costs that has to be factored in when dealing with any sort of transportation work is fuel. The large fluctuations in diesel fuel prices - especially in recent times - many choose to buy in bulk, storing the fuel they need for their trucks on-site, yet even this has a cost attached to it.

www.goldeagle.com

As I was doing some research about how long DEF lasts there is a temperature constraint, if it gets hot then yes it reduces the life. The question is how hot is your DEF with the tank in the engine compartment? I don't believe they put DEF tanks near the engine in autos, in my 2017 Newmar Ventana the DEF tank is right near the Cummins diesel engine which gets very hot and it's also on the side of the coach, opposite the exhaust, where the after treatment (regen) occurs, which gets extremely hot. Bad location for DEF tanks? Possibly.

 

[Neal]

It’s frustrating how much divergent information is circulating on this topic. At FPU, my tech said to keep it at the 75% full level. At the latest AIM rally, a Freightliner rep said to keep it full. I’m going to begin keeping it as full as possible per the FL guy. We’ll see what happens with that.

It is frustrating and we never know who to believe. The tech’s aren’t RVers and I take with a grain of salt the various sources. There was an RVer that was told by a Newmar tech to use the small (3/4” garden hose port) on the end of the sani-con. I tried to explain no, that’s wrong, that is going to give you a lot of backpressure but they believed the tech but eventually changed to the larger port on the end of the sani-con. The same goes with tire pressures, every different shop service worker has their opinions. Even RVSEF (or whoever they’re called) that I paid for corner weights gave me their opinion on tire pressure instead of chart data. I didn’t pay for an opinion on tire pressure, i was not happy! Do we need palm readers next?

Collect the data and opinions, research, make your decisions based on the aggregation of info and who you want to believe. We want to believe some of these techs should know, I’ve learned otherwise.

 

[Joe Dutchstar]

This thread is very interesting to me in a theoretical sense.
Urea is a dissolved salt and as such will crystallize as water in the solution evaporates. Crystals will go into solution once rehydrated.
However many floats on DEF headers have become stuck as DP sits with half filled DEF tanks due to crystallize urea on moving parts from what I have read.
DEF will freeze and expand by some 7%. Not sure how sensitive the DEF delivery system is to freezing fluid.
Needless to say DEF is a fluid that needs to be managed.
As with most systems in a diesel they “need” to be operational on a regular basis. Fluids consumed regularly.
As we all know, sitting parked in storage is the worst thing for large machines.
Testing urea concentration at the pump is not so convenient nor at the store checkout.
On top of that a very complicated delivery system that is temperamental doesn’t help.

Solutions: in my opinion first step is to understand the system and how to determine issues, next buy DEF from reputable suppliers with care, ( sealed containers or fuel stops with maintained pumps), then regular maintenance from a knowledgeable shop.
And of course fingers crossed things don’t go wrong.?

 

[Neal]

I agree and I think we all operate with paranoia of the DEF crystallization. But if we are given the “recommendation” of letting it go to 2 dots until refilling, then it probably wouldn’t matter to go to 1 dot. Some people run full all the time, FL gives the guidance to go to 2 dots then refill. That’s what I do 99% of the time. On the way home I wanted to go lower to get more “fresh” filled and let it sit on 2 dots (half) for a longer time, wasn’t long enough as it was only just below 1/2 on the tank gauge. For whatever reason my coach uses very little DEF, it is very efficient for whatever reason compared to others. I think if you’re going to let it run down further then carrying a box of DEF would be good practice in case crystallization becomes a problem. But again, at what level does this become a problem? Where are the parts affected? Are they at the top? bottom? 3/4 way down? If they are at the bottom then why would any level matter other than above this point? We all tend to make assumptions on these things and none of us know the real answer without looking at a diagram of the tank and internals to understand where these parts of concern reside.

 

[Neemer]

I’ll buy the house a round when we finally get to a place that DEF header issues are in the rearview mirror. Something else will come along, but hopefully whatever it is doesn’t strand anyone beside the road or kill an entire summer travel season. This mess is is just that: a mess.

 

[Neal]

The topics have converged, this thread really isn’t related to the DEF head issue but it made me decide to voice concerns I’ve had on DEF management and my thoughts on tank level management. I’ve been a “victim” of peer guidance on how low to let DEF go before refilling, I’d like to get to the bottom of it (pun intended).

 

["EZ"]

That statement appears contradictory to me. If shelf life is affected by high temps, then it must also affect quality. Unless quality falls off the edge of the table at the end of shelf life, there has to be a degradation curve. I’m not taking issue with you, EZ, but I’d like to see some real data on this. Two years is a long time. What exactly is the impact? Halved? Worse?

Back in 2010 when I sold my FIRST Ram 3500 with DEF our shop didn't know they were supposed to fill the DEF tank during the PDI. I delivered the truck to the customer and they took it out of town on a job the next day. The DEF light came on so they stopped at a parts store 100 miles away and bought a couple jugs of DEF that was sitting in the front window on display (remember, this was all brand new technology). They got about 10 miles away and the truck shut down. We had to tow it from Knoxville TN back to Chattanooga TN to fix it in our shop because it was brand new and only had 110 miles on it! Turns out the DEF fluid they put in it was bad. The short time it had sat in the window of the parts store in the full sun was enough to kill the DEF fluids shelf life. Hard expensive lesson learned. DO NOT let your DEF sit in the heat any longer than you have to. Store it in a cool dry place, or you too may have to be towed................

 

["EZ"]

The DEF tank has a heater. Not sure what temp it heats to.

It keeps it from freezing.

 

[Neal]

Back in 2010 when I sold my FIRST Ram 3500 with DEF our shop didn't know they were supposed to fill the DEF tank during the PDI. I delivered the truck to the customer and they took it out of town on a job the next day. The DEF light came on so they stopped at a parts store 100 miles away and bought a couple jugs of DEF that was sitting in the front window on display (remember, this was all brand new technology). They got about 10 miles away and the truck shut down. We had to tow it from Knoxville TN back to Chattanooga TN to fix it in our shop because it was brand new and only had 110 miles on it! Turns out the DEF fluid they put in it was bad. The short time it had sat in the window of the parts store in the full sun was enough to kill the DEF fluids shelf life. Hard expensive lesson learned. DO NOT let your DEF sit in the heat any longer than you have to. Store it in a cool dry place, or you too may have to be towed................

I'll continue to use truck stop DEF over boxed DEF. It's underground and not in sunlight, it's constant temp (56 degrees I believe), or at least some cool consistent environment, and there's turnover. If it was bad a lot of customers would be affected, same with the diesel coming out of the pump, a situation any station cannot have happen. Boxed DEF has too many unknowns, I'll avoid it unless emergency use.

 

["EZ"]

I'll continue to use truck stop DEF over boxed DEF. It's underground and not in sunlight, it's constant temp (56 degrees I believe), or at least some cool consistent environment, and there's turnover. If it was bad a lot of customers would be affected, same with the diesel coming out of the pump, a situation any station cannot have happen. Boxed DEF has too many unknowns, I'll avoid it unless emergency use.

Smart plan Neal.

 

[FL-JOE]

I think Neal summed it up pretty good, no matter if you are in a large DP or a 1-ton PU truck with DEF. Use the freshest product you can, which will generally be bulk from major truck stops, and try to manage your levels according to your usage. In other words, don't sit in the Florida Keys for 8 months with a full tank of DEF.