Do you keep your DEF fluid topped up or just refill when the light comes on??


Asked by Sep 07, 2017 at 03:35 PM about the 2011 Mercedes-Benz Sprinter

Question type: General

If you have any experience with this either way, please share.

The owner's manual says if the light comes on, refill and the system will reset
itself.   Dealership says keep it full.

What's your opinion???

30 Answers


Its like checking your oil and other fluid levels, you do not want it to go dry, I would start at 1000 miles checking and see how much you use, if its not too low check again in 2000 or 2500 miles and figure out how fast it goes bye bye, I would top off before it reaches 1/2 gone. Depends on your driving habits, if going on a long trip in nice clothes then top it off before hand so you do not need to worry about while on the trip. Should be able to make it 4000 miles or so. If your pulling a travel trailer then check more often and keep some on-hand to top off, and the top off mentioned means just that its top off fluid so top it off instead of waiting till its empty.

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When tank reaches 10% full the light on dash flashes and this is fine to wait to fill and the standard but as with any system mul-functions occur. So check for yourself if possible. There is 3 safeguards in place most times first amber light on then it blinks then red light on dash stays on and engine is limited to low power until refilled.


"Want to prevent disruption? Watch for the signs & keep the tank full." look at this page.

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enginecreator- THANK YOU ! Actually, I drove about 3,000 miles and the light came on. I expected that this would be easy.. just put in 2 or 2 1/2 gallons of DEF fluid and the system would reset.... didn't happen.....the light stayed on and the vehicle started.the countdown mode....had absolutely no choice but to take it to Mercedes Benz. They reset it and of course charged me for the service...and told me that I should keep this filled up and check it every one thousand miles. When I purchased the Sprinter someone told me I could easily go 4,000 miles or more..and just add fluid..... Mercedes Benz dealership said don't let the light come on and keep it full..... I'm going with the dealerships advice from now on. My frustration is that the owners manual says one thing while the dealership says something..... very confusing.

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Thats what I say most say add when first light comes on but I have heard of the system errors and topping off is best. These were designed to not mal-function of course, but sometimes have to be reset by the dealership and this is my take on it, if it may mal-function if the light comes on then keep it full.


enginecreator- Sure, I understand....and believe me, within a couple of miles, literally just happened that close to home, I added almost 2.5 gallons of DEF and I really expected the system to reset itself just like it states in the owner's manual... when this failed, the system gave me the error message STartes RE with a number like 5 out of 9...... Called Mercedes Benz and they said bring it in before it gets to zero, otherwise, it will have to be towed.... Didn't want that.... they checked my system said everything looked fine, didn't overheat the DEF, no contamination.... just needed to be reset... cost me $195...did I like it ...NO.. but, what are my options??? I've read countless stories online where people failed to get their systems running with all sorts of "tricks"....none of them worked and they couldn't restart....... From here on out, I'm going to follow the dealerships advice and ad fluid every 1000 or so miles... that's what they said to do......I only wish that the stupid idiot light was never discussed in the owner's manual and should have ignored the instructions someone gave me when I purchased the truck. You live and learn....


Sounds good (keeping it topped off every 1000 miles and never under 1/2 full.) I know of the stories, I would consider filling a complaint. Its a known issues that needs a recall order filed by the GOV to force Mercedes to fix and reset as needed no-charge or fees other-wise it will never be resolved and will be a piggy bank for them here on out. Also there are issues of it thinking its empty when its not and needs another $195.00 reset and it not working correctly and then needing to be replaced or parts of it anyway (pricey) so hope/wishes the best for you.

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Best Answer Mark helpful

enginecreator- I just marked your last answer "best answer"...YES, I will definitely top it off every 1,000 miles....and thank you for sharing this with me... question,. I would love to see some of these stories you speak of...if they're in writing or maybe you have just been told... actually, I believe you! What was very interesting and frustrating to me is that the dealership says one thing and the owner's manual says something else.....No matter how you look at it, the message is VERY INCONSISTENT. That's not first class world service you might expect from Mercedes Benz... Looking forward to hearing if you have any website link to these discussions.--Mark


From the mechanic's view Mercedes is too wrapped up in building client list by forcing them to come back to them for every little thing which is intentional, one thing to build a good car and everybody wants it, but instead their parts cannot be rebuild must be replaced with new parts, they do not provide repair manual to Auto-mechanic class rooms or provide any tech answers for the shops to work on their cars, because they claim full rights to work on their cars and shrug their shoulders to mechanics with you can not fix them, but we can if they were built to be fixed in the first place. The DEF fluid being contaminated is a way for Mecedes to void the warranty on it, We as consumers to not control the quality of DEF fluid but our Country does but this is not their Country so all they have to say is "contamination" then hand a bill to you for $2800 to (not repair) replace it. Its not built to last, its built to keep making money from you after the sale.

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A friend of mine owns a Mechanic shop that used to work on all Cars he went to mechanic schools and he was approved by Mercedes (picked) to go to a Mercedes only school which also sent them the Germany in the 1990's he came back worked at a Dealership (think it was a ten year contract) he took his profession to his family shop and they worked on Mercedes only for about 20 years, cars he learned on are the older cars now, so they are now fixing all types of cars again, I go by there I see Mercedes sitting around in line to be fixed or waiting for parts or should I say for their owner to come up with the money to buy those parts. I have heard some of the stories/complaints.


enginecreator-. I had a couple of probing conversations with two different service advisors and one Sprinter technician... Here's what I know... there's some disagreement with whether to keep the DEF tank topped off or let the light come on and refill....the owner's manual says it's OK to wait... Remember, my situation was that I drove 3,000 miles, refilled with just more than 2 gallons..the tank according to the technician is 5.5 gallons..SO, their contention that I allowed my DEF fluid to run "low" is really a stretch.. I'm going to just keep adding DEF fluid every 1,000 to 1,250 miles from now on. I also reminded them and they confirmed that the Sprinter is under a Federal Emissions Warranty for 8 years or 80,000 miles.... my vehicle is six years old and has 29,000 miles....I will pursue this more with them if it arises again... believe me.. And, my vehicle is NOT something you just turn in for a new's a 2012 Roadtrek RS Adventurous...a converted 2011 Sprinter 3500 on the 170 wheel base.... here's a picture of it below...

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Looks great Markw1952 I'am happy for you.


Thanks....I'm retired and almost 66... I learned several years ago that life is short and people "overestimate" how much time they have Dad died earlier than expected.... My father in law retired at 55..."told me that he did it to enjoy his retirement", great answer.... Anyway, you can't take it with you.. just enjoy life... therefore, I can't get too excited about little speed bumps like DEF fluid...if you know what I mean..? Here's a cool picture of the inside of my rig... we're just going to enjoy it as much as possible... And, the fact that it's a diesel, I'm hoping that it will go at least 300,000 miles...


Here's a better picture...


My grandmother lived to 104 & 1/2 years. Born on a Holiday died on a Holiday. Her & my grandfather loved to travel. RV'ing & campers on all the lakes & rivers and parks around here, well with-in 700 miles from here I think is about as far as they went, which they saw and did from the Beaches to the mountains, We went some too, and some of my best memories.


Looks nice. Since your at the age my grandfather was when he was doing the Camping I thought I would tell you how he did things. He buy a rv or camper that needed his touch and My grandmothers she did all the interior upholstery with her older style industrial sewing machine and he did all the customizing, inside & out, updating it, cabinets, appliances ect. Then take it too a camp ground with a lot of people there, put out ad in paper there and tape up for sale signs and go looking for another one to flip, he would rent a lot big enough for two campers/rv and buy another, pull out his tools start working, and folks would ask him to do work for them and while doing so he was getting the other one ready to stay in if the other sold and put for sale on it too, and crappie fish at night, most times he sold at least one and if neither sold he made money for work he did for others and then pull one to another spot, he was always updating one and selling another one and kept 3-5 set up in different places to use and sell, so they were going back and forth from lakes mostly or different spots on the same lake. There are some marinas I know he did too but I have been camping at every lot they had to rent, He did similar with boats too, he would visit the dry docks and buy one set it up for fishing and for sell use until it sold, but kept them at the lakes he was at except a few times I remember seeing a few at their house. He always had at least one camper/rv at home he was getting ready to sell. Some of these he completely remodel and others just got new upholstery and appliances and general fixes/updates. He knew everything about them and I remember him fixing or doing work on other peoples campers at parks, it was like they were just drawn to him so he always had work and more campers to sell, If they needed work or the people did not want pull it back home he would offer to buy it. During his time the campers /rv's were basic then to modern so he modernized many of them and made them nicer and put them places somebody wanted to have one at which seemed to work very well for him. My grandmother was a expert with that sewing machine. She did alot of work herself. They did this for 30+ years.


enginecreator- thanks for sharing your stories.... I'm not the handy type... just want to explore and enjoy for a while.....and I have no illusions of making money or even breaking even.... Again, it's more about the experience of doing it .. we purchased the rig pretty much as you see it and had to immediately put on new tires, batteries and some other things... All maintenance items... PLUS, some key make it safer.... With 18 MPG, it's not too terrible ..

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!8 mpg not bad at all, Your welcome & thanks too, have fun.


enginecreator- Happy New Year... My friends at Mercedes.. tell me that it's necessary to drive at least 2,000 miles before filling up the DEF..... otherwise, it may overheat the DEF system.... Just FYI. We'll see.....

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Happy New Year.

I have a 2011 Winnebago Via ... Sprinter 3500 chassis and engine. I put four gallons of DEF in it about 8 months ago . The light did not come on at that time. I have done about 10K miles since then and the DEF notification came up a week or so ago. I have put five gals of DEF in it and the light has gone out. It all seems to be OK.

I just put 2000 mi on driving west from New England. Stopped in a Wallmart for the night and bought 2.5 Gal. Box. Will fill / top off in the morning and give the extra (if any) to the other Sprinter in the ‘camp ground’


IanCmrn- Thank you... I think my DEF tank is a 4.5 gallon tank...they also had 3 1/2 and 5 1/2 gallon mine is the middle sized tank... If you added four to five gallons you definitely have the larger tank.... SO, are you saying that your DEF light came on..and you refilled the tank and the system successfully reset??? That's great... My 2011 Sprinter 3500 like yours recently had the entire emissions system replaced..under warranty...yes I said UNDER warranty... you see, the emissions system is under a federal warranty for 8 years or 80,000 miles... I know your RV...I saw one at a campsite a few years ago...nice rig... Mercedes Benz advised me to just keep driving and fill it up when the light comes on.. makes me a little nervous.. since the last time this happened..the light didn't go out...had to take it into Mercedes and they charged me $195 to reset my system.. Maybe with the new emissions it will work as expected?? Tell me, how many miles do you have on your 2011 ...and has it cost you a lot for maintenance... I currently have just over 40,000 miles... went on a cross country USA trip.. almost 11,000 miles... ONE thing.. since I purchased this at 26,000 miles... hasn't used any oil at all... amazingly smooth turbo diesel.... never slows down for anything..climbs mountains easily... few weeks 22 MPG..on flat ground... overall 18 to 19 MPG.. I imagine you may be getting a little less...15 to 16?? Your rig is larger... I'm envious of your extra space... your rig is a small Class A... Otherwise, I think you have the same chassis and drivetrain as my rig....3 litre V6...and 5 speed triptronic automatic...? What's the weight of your vehicle... OK, 10,000 miles would translate to 1 gallon for every 2,000 miles... pretty good....I must have had a failing.. obviously it did fail on the last leg of my 10,500 miles trip... kept adding DEF fluid the whole way... kept using it and going down the whole time... I'm kinda surprised that there's no DEF guage on my vehicle.. only the warning light.. BUT, overall, I really do like my RV... here's another inside picture...small but deluxe... Finally, how is your rig driving in high winds?? We found it pretty stable with electronic stability control... but, we could still feel it a little.... overall, the coach is pretty quiet...

MarkW ... Yes my tank must be the 5 1/2 gallon one. Supposedly the "Check DEF" notice comes up at 10% left. That would be about 1/2 gal. I did have a problem with the engine light coming on then going off after a couple of days. That kept happening and the Mercedes dealer (Warner Vans of Utah .. we live 1/2 way between Denver and Salt Lake City. We prefer the Salt Lake City dealer ... great folks) could not find the problem. They eventually replaced the NOX sensors under warranty. We bought the unit a year ago at 35k miles. We had the oil changed at that time and had the transmission oil changed at 40K. We are now at 52k and plan on changing engine oil, filter etc. at 55K. The only other issues we have had is the engine light came on when were in Pennsylvania. I took it to a dealer in Harrisburg and the found a broken wire at a plug going to the NOX sensors. They repaired it ($400) and I have had no further issue with that. My insurance paid for that. I also had a steering fluid leak ... very slow. That turned out to be a clamp that needed tightening. Apparently, that is not uncommon. Make sure you get the right fluid if you have to top it up. We LOVE our rig. It is very much the same as the Navion class C rigs from Winnebago except up front. We love the room in the cockpit and the big front window. We get up to about 18mpg if we keep the speeds around 60-65mph. We usually run faster ... 70-75mph and the fuel consumption goes up ... 14.5 - 16mpg. Driving in high wind does require keeping your eyes on the road but my Lexus SUV does too. When we came back from Pennsylvania we hit it all ... Rain, sleet snow and wind. Big time wind. Our rig handled it all without any problems. I notice in your picture you have a Dometic cooktop with a glass lid as we do. On ours the glass lid exploded. I have found that this, while not common, can happen with tempered glass. It is nothing that you do, it just happens. Sounded like a gun shot.


Hi Ian, just sent you a private email... Forgot to mention and comment on the tempered glass... yes, we have that Dometic cooktop... we're pretty careful about letting it cool BEFORE we close the lid....and the Dometic refrigerator is very small.. 3.5 or 3.7 cubic feet..we carry an additional YETI 2 bag in the coach.... I'll be extremely careful with the cooktop, thanks.. Check the message I sent......MARK


James, welcome.... what's your rig..?? Model and size?? Mine is a Class B... while Ian has a small Class A.... probably 25 or 26 feet... my Sprinter is 23 feet ...

I have a related question... doesn't DEF go bad? A friend and I did some online looking and it appears its life is only rated up to 90 deg F. Surely, in the summer in most of the country, the engine compartment is much hotter than that. Seems like keeping the tank topped off is a sure way to have that fluid get old. Seems it would be better to let it run low and then add, and NEVER top it off. Before finding out about the temperature sensitivity of DEF, I had been topping mine off (2012 Sprinter 3500), but now think I should intentionally let it run low. I haven't put enough miles on it to get to the point of the warning yet. Also seems that if the light won't go out when you follow the manual, you have reason to claim that it is a warranty defect the dealership should repair for free. I also haven't had my unit long enough to get to know the dealer yet.

I have a 2014 sprinter Evans had similar issues with def light coming on. Added fluid and it would just stay on and then sometimes it would go off,it eventually gave me the 9 restarts left message. Took it to dealership and they said everything was fine just needs to reset sensors, cost me a couple hundred. By the way I live about 2 hours away from dealership. So when I drove it home I parked it and then 2 days later I started it up to go on a trip and got the check def fluid light, this was a little unnerving because dealership said they had filled tank. Filled up with diesel and added a little fluid apparently it didn't need much it overflowed. I drove it anyway for about 700 miles and added 2 gallons of fluid and light never went off. When I got back home I took it back to dealership and they told me that I had run the def tank dry which was not true but because of that they needs to replace the heating element and the delivery pump. Mercedes said they would not pay for that, I have 15000 miles on it. My extended warranty would not cover it either because it does not cover emissions so I had to pay 3700 dollars for repairs, needless to say not happy about that. So we are scheduled to go out on a trip in a couple days we will see how it does. I just don't know when to check for adding fluid so I'm glad I found this article, think I will check every 1000 miles also


There are 3 sensors in the D.E.F. tank. One at the top and one 3/4 of the way down and nearly empty. If you don't hit the top sensor the vehicle will not sense that you are full so it will drop down to the countdown clock. Just make sure when you fill it that you fill it all the way to the top even overflow it just so it can reset itself. Good luck and happy motoring.

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