Real World DEF Experience

[RedT]

Hopefully this subject is in the correct category. In shopping for a newer motorhome, the DEF subject has been highlighted. I was only mildly interested about DEF since it is not applicable to my 2003 Caterpillar engine engine, but the current Cummins engines all require DEF.
So how much "hassle" factor is associated with DEF? Is the DEF head issue prevalent, or the squeaky wheel? What is your real world experience - is DEF a significant factor in operation of your motorhome?

Any specific do's or don'ts?

[Solo_RV_Guy]

Originally Posted by RedT

Hopefully this subject is in the correct category. In shopping for a newer motorhome, the DEF subject has been highlighted. I was only mildly interested about DEF since it is not applicable to my 2003 Caterpillar engine engine, but the current Cummins engines all require DEF.
So how much "hassle" factor is associated with DEF? Is the DEF head issue prevalent, or the squeaky wheel? What is your real world experience - is DEF a significant factor in operation of your motorhome?

Any specific do's or don'ts?

You will not escape "DEF" in any new diesel, on-road vehicle. End of story.

DEF, by itself, is not an issue. The most current problem was multiple batches of bad DEF head sensors or analog/digital converters built onto the sensor package. The early generation of sensors that only monitored a couple of parameters have had age-related failures but nothing like the more current sensors that measure multiple things.

Most of the bad sensors/AD converters in RVs were made or distributed by Shaw Development in Florida, and were used extensively by Spartan (Freightliner mostly used a different product). Even Volvo/Prevost has had sensor problems crop up.

That all said, the rate of new complaints about DEF sensor failures and resulting de-rating of engine performance have dropped to near zero here on iRV2. Some owners have replaced DEF heads multiple times, others are still running on OEM parts. The "Gen 7" Shaw parts appear to have addressed whatever problems Shaw had in Gen 5 & Gen 6 sensors.

There are also some "Chicken Little 'the sky is falling'" comments here about DEF availability in stores like Walmart; it seems to be geographic. When I stop at AutoZone, Tractor Supply, or Wallyworld, there's plenty of DEF stacked up, but I'm not on I-95... There have been zero reports of DEF shortages at truck stops.

Of all the stuff that can go wrong with a new RV, DEF is currently the least of my concerns. Lousy construction, cheap materials, and incomplete assembly would be at the top of my list.

[greeneville1]

The Def Systems on newer coaches add a possible problem that will ruin a RV Trip in a heartbeat. We have had 2 DEF fault codes appear to our rvs. One on a 2019 Tiffin Bus and recently our 2021 Tiffin Bus. Each appeared out of the blue with no apparent reason. In both cases the DEF system was working as designed but the DEF sensor that monitored the DEF fluid failed. Shaw Industries in Bonito Springs, Fl. is the DEF Sensor for alot of Spartan and Powerglide (Tiffin ) chassis and cannot seem to make a truly reliable sender.
If you have a DEF fault code arise, you can almost count on at least a couple of days down time while chasing a new unit and install. That is our negative side of the DEF system . The positive side to the system is now how much cleaner the diesel engine burns fuel. No more stinkpot smell from the exhaust. Another benefit, so I am told is the better fuel economy that the new diesels are acheiving. Some Cummins Techs attribute this to being able to better tune the fuel /air ratio of the diesel now that the aftermarket Def system and converter are removing the bad stuff. And if you fall in love with a newer Def RV, some folks have simulators to install in place of a failed DEF Sensor to fool the engine computer into seeing a correct input from the failed sensor. Some folks even have two simulators but that is a rumor which we have no proof. Find something that you both love and drive the heck out of it. Please stay safe.

[dizcom]

It isn't a hassle. It isn't much of anything really. One more container to keep from being empty. You can get DEF where you get diesel, a lot of times, right at the pump. Otherwise, just in the store in 2.5 gallon jugs that you pour in when you get around to it. Some people carry a spare, we have and we haven't, mostly haven't. We haven't had a head go bad on us, but we carry a simulator, just in case. Getting stranded seems to be mostly a thing of the past now.

[Cat320]

DEF is like going from leaded to unleaded fuel. It is mandated by the gubmint...put it in and keep in trucking. I've had no trouble with it. However, it does have an expiration date, which should be followed. Bing/google DEF and it will tell you all about it.

[Archer2]

In my opinion the unusual (relatively) high number of DEF sensors failing in the 2016 and newer coaches was not the real problem. A failed sensor was just like any other moderately annoying system failures that can happen at any time. The thing that turned a simple failure into a major problem was that the replacement parts were unavailable and nobody could even guess when they might become available again. It appears from anecdotal evidence that the supply-chain problems have abated and people are now reporting 24-72 hour turnaround time for repairs.

[Winger2]

Originally Posted by dizcom

It isn't a hassle. It isn't much of anything really. One more container to keep from being empty. You can get DEF where you get diesel, a lot of times, right at the pump. Otherwise, just in the store in 2.5 gallon jugs that you pour in when you get around to it. Some people carry a spare, we have and we haven't, mostly haven't. We haven't had a head go bad on us, but we carry a simulator, just in case. Getting stranded seems to be mostly a thing of the past now.

Exactly.
I see so many with older coaches making a big deal about DEF coaches. Then, in the another thread you will see the problems they are having with an older coach.
Everything is relative. If someone wants an older coach they should get it. But remember they are dated. The newer you get the less chance of the older items reaching their lifespan.
I would not let the naysayers win. They should find the floorplan that they like with the options they like older or newer. There are many great older and newer coaches out there

[Mr.Mark]

My 2015 Prevost had DEF and no issues in the 6.5 yrs. that I owned it and drove it 63,000 miles.

My new 2021.5 Pleasure Way motorhome on a 2020 Mercedes-Benz chassis has had no issues either. I'm at 14 months of ownership and 9,700 miles.

Safe travels,
Mark

[PDR John]

We had a 2013 Newmar Dutchstar for 7 years and over 70,000 miles, DEF wasn't a real issue.

My personal issue was chassis builders attitude towards it (back then). Just because it is government mandated doesn't mean you have to make it a pain in the ass to use.


They set the filler so far back that you had to use a long extension tube just to fill the tank. Unless you could find a station with a DEF pump, which in late 2012 was not very common outside of major stations.

But then you had another issue, the DEF fill was on the passenger side rear of the coach. So you had to go through the truck lanes backwards, or use the pump in the other lane.


So if you're looking at a coach that requires DEF, just make sure the filler is as easy to use as the fuel filler. Then enjoy your RV while cruising down the road.

[High Road Travelers]

Originally Posted by dizcom

It isn't a hassle. It isn't much of anything really. One more container to keep from being empty. You can get DEF where you get diesel, a lot of times, right at the pump. Otherwise, just in the store in 2.5 gallon jugs that you pour in when you get around to it. Some people carry a spare, we have and we haven't, mostly haven't. We haven't had a head go bad on us, but we carry a simulator, just in case. Getting stranded seems to be mostly a thing of the past now.

It may not be a "hassle", but in the two years that I had a 2016 diesel motorhome, the DEF system left me at Freightliner service centers four times. After the fourth issue (each issue left me sitting for 2 to 4 days) I traded it in on a gas motorhome and have never been concerned about a breakdown since. Just my experience, and of course mine may have been a lemon.
Thanks,

[Crasher]

In 85,000 miles and 9 years with our 2013 Bus, I have had one sensor fail that cut the power to 75%. Easily drove to our truck service center where they replaced the sensor. Mine takes a gallon of DEF every 380 miles so I buy it three times a year. I had read of later models having "Head" failures. so I purchased one to carry along just in case. Of course we all know now that I have a spare along, the original will never fail. I would not let any potential DEF issue influence my choice of motorhomes. It's just not a big problem.

[RVFunlovers]

DEF is like one more fuel gauge to key an eye on. But it last longer than diesel.
I fill up DEF every 2 or 3 times I fill up diesel. I don’t let it get close to empty.

If you use truck stops like I do you may have to fill diesel then move forward about 30 feet and then add DEF. My fuel tank is near the front. My DEF tank is near the back.

I find this far easier than jug DEF. The DEF does add some cost and hassle but not by a big percentage. It helps cut down on pollution so I do not mind it.

Now when the control system (DEF Head) shut’s down and derates your engine that is another story.

Some people carry a share or an emulator to bypass the DEF head in an emergency.

[UTTransplant]

We used DEF in our pickup for 3 years without any issue. We have used DEF in our motorhome for 4 additional years. Seven years without issue on two different types of vehicles. We fill up our tanks at the truck stop, just like we fill up with fuel. There are a few older DEF rigs with the fill on the passenger side, and those are more pain. You pretty much have to use the bottles then, and the plastic waste is huge. We drive a lot though, and our DEF stays fresh. If you leave a DEF rig sitting for 6-9 months in the hot Arizona or Florida temps, you might want to check the DEF quality before driving though.

Oh and the “DEF Head” issue you hear about is almost exclusively on Spartan and PowerGlide chassis rigs. Freightliner DEF heads have a completely different design. While any electronic component on a MH can go bad, it is a rare thing on a FCCC chassis. Even if it happens, you get notice and can get a reprogramming from Cummins to keep you on the road until a part is available.

[DaddyRV779]

Last week my Def Quality warning came on in my 2019 GMC 3500HD DRW and told me to fix it in 100 miles or it would reduce speed....yeah it had been a while since I bought DEF, at a truck stop....Made it home okay and added a box of DEF Premium - warning went away...sure glad my truck can tell me when when it's UREA is �� BAD... Because I am not checking it - OH YEAH ...heck GMC doesn't even provide a gauge in my model ... Its just OK, or add in 100 miles or you cannot drive that fast. Nothing against engineers, but come on - why did it take so long to invent an accurate gauge and move the D E F filler to the driver side Diesel filler area? Some dumb ass engineer probably read these posts, made a suggestion, got a promotion, and is about to buy a new truck they know is built better ��