Do you add DEF fluid in between service intervals..?

Roadtrek Adventuous RS1 · 05-18-2018, 06:32 PM

Service intervals is every 10,000 miles..and we have a 4.5 gallon DEF tank...
Late last year... Mercedes Benz replaced the entire emissions system on my Sprinter 3500...

There's no DEF guage.. which always bothers me.... before we had the emissions system replaced.. seemed like it went through a lot of DEF...and one time the low level light came on ... which is similar to your low fuel light.. BUT, even filling up the DEF tank..the system did NOT reset itself and went to limp mode with limited restarts... had to take it to Mercedes...

Now...2,000 miles past the new system install...one person from Mercedes said... just keep driving until the light comes on again... should work fine...

What do you think... should I just believe that??

I have to take it in for service in about 2,500 miles.. again, he claims that I shouldn't need DEF between services... and that they will replenish the system when I bring it in....

I sure don't want another limp mode and limited restarts...it's an ugly countdown ...and once that occurs... your stuck taking it to Mercedes right away.....??

Comments please...

ponti33602 · 05-18-2018, 06:43 PM

Quote:

Originally Posted by Roadtrek Adventuous RS1

Service intervals is every 10,000 miles..and we have a 4.5 gallon DEF tank...
Late last year... Mercedes Benz replaced the entire emissions system on my Sprinter 3500...

There's no DEF guage.. which always bothers me.... before we had the emissions system replaced.. seemed like it went through a lot of DEF...and one time the low level light came on ... which is similar to your low fuel light.. BUT, even filling up the DEF tank..the system did NOT reset itself and went to limp mode with limited restarts... had to take it to Mercedes...

Now...2,000 miles past the new system install...one person from Mercedes said... just keep driving until the light comes on again... should work fine...

What do you think... should I just believe that??

I have to take it in for service in about 2,500 miles.. again, he claims that I shouldn't need DEF between services... and that they will replenish the system when I bring it in....

I sure don't want another limp mode and limited restarts...it's an ugly countdown ...and once that occurs... your stuck taking it to Mercedes right away.....??

Comments please...

We have a bit of OCD around this........we had and top off every 4-5 tanks of gas......not sure what it takes....haven't measured but like to top off. :<

avanti · 05-18-2018, 07:00 PM

This has been extensively debated over at Sprinter Source.

I used to be in the "wait for the warning..that is what it was designed for" school. I have been persuaded otherwise. There is a theory around (first proposed by a knowledgable source) that the "low def" warning somehow triggers a bug in the DEF-system firmware such that error conditions occur that otherwise would never have happened. I know that this sounds like typical Internet BS, but: (A) the source is an unusually reliable one, and (B) there have been SO many reports of countdown conditions immediately after warning-triggered DEF refills. It happened to me, and apparently to you as well. There are numerous others.

SO, I now top mine off every 5K miles or so. There is little downside, so why not?

Roadtrek Adventuous RS1 · 05-18-2018, 10:05 PM

Quote:

Originally Posted by avanti

This has been extensively debated over at Sprinter Source.

I used to be in the "wait for the warning..that is what it was designed for" school. I have been persuaded otherwise. There is a theory around (first proposed by a knowledgable source) that the "low def" warning somehow triggers a bug in the DEF-system firmware such that error conditions occur that otherwise would never have happened. I know that this sounds like typical Internet BS, but: (A) the source is an unusually reliable one, and (B) there have been SO many reports of countdown conditions immediately after warning-triggered DEF refills. It happened to me, and apparently to you as well. There are numerous others.

SO, I now top mine off every 5K miles or so. There is little downside, so why not?

Do you see any downsides to topping off every 2,000 miles??

avanti · 05-18-2018, 10:18 PM

Quote:

Originally Posted by Roadtrek Adventuous RS1

Do you see any downsides to topping off every 2,000 miles??

Only that it is 2.5 times more work than 5,000 miles, and I know of no data suggesting that there would be any point to it.

I guess there is also the fact that every time you remove that cap, you are risking contamination.

Davydd · 05-19-2018, 03:55 PM

DEF doesn’t last 10,000 miles before the light comes on, so adding practices are up to you, but you do have to add. When the light comes on we go to the nearest Walmart and buy and add their 2.5 gallon container. They have a built in spout. Easy enough to do. Most good dealers will top off your DEF tank at the service interval. It depends on your driving but we get close to 8,000 miles between adds. We might top off our tank at the beginning of a trip just out of convenience but storing DEF is another no-no. So you are going to buy fresh anyway and the same inconvenience as on the road.

XLent · 05-19-2018, 04:06 PM

I top mine up before a trip. Be careful and don’t spill. If you do spill; clean carefully and completely.

Roadtrek Adventuous RS1 · 05-19-2018, 04:26 PM

Quote:

Originally Posted by XLent

I top mine up before a trip. Be careful and don’t spill. If you do spill; clean carefully and completely.

I noticed that since I've had the emissions system replaced under warranty...the DEF usage has gone way down... that's a good thing..

604eholston@charter.net · 05-23-2018, 06:15 PM

I, too was frustrated by utilization of DEF, bought coach used and had no knowledge of any replacement. I had installed a Scan Gauge 11 and heard that it could be programmed to read out the status of the DEF tank on my Mercedes-Benz Sprinter 3500 van. It's a Winnebago ERA, 2015. Sure enough on the IVR2 forum a fellow had the codes and I was successsful in programming the device to readout the percentage of full in the DEF tank.
Now I know how much of the d--- stuff I have left.

Mfm · 05-23-2018, 06:17 PM

Quote:

Originally Posted by Roadtrek Adventuous RS1

I noticed that since I've had the emissions system replaced under warranty...the DEF usage has gone way down... that's a good thing..

I add DEF all the time...had the light go on an hour or 2 outside of Las Vegas on a weekend and was stranded in Vegas until the Henderson dealer opened up Monday. The low DEF somehow triggered a software issue as well as having 2 bad sensors. Had one of the same sensors go bad a short time later when back in California.

avanti · 05-23-2018, 07:14 PM

Quote:

Originally Posted by 604eholston@charter.net

I had installed a Scan Gauge 11 and heard that it could be programmed to read out the status of the DEF tank on my Mercedes-Benz Sprinter 3500 van. It's a Winnebago ERA, 2015. Sure enough on the IVR2 forum a fellow had the codes and I was successsful in programming the device to readout the percentage of full in the DEF tank.
Now I know how much of the d--- stuff I have left.

I hadn't heard about this. Very useful. Could you share the details?
Thanks.

buzzard28 · 05-23-2018, 11:18 PM

On My 2016 3500 the level can be seen by using the button on the steering wheel. I fill mine at 1/4.

chausjm · 05-23-2018, 11:29 PM

Just top up every 400 miles or before each trip. If you don't you will run the risk of your engine light coming on and then you will have to have it serviced to reset the engine light.

avanti · 05-24-2018, 12:27 AM

Quote:

Originally Posted by chausjm

Just top up every 400 miles or before each trip. If you don't you will run the risk of your engine light coming on and then you will have to have it serviced to reset the engine light.

I agree with keeping the warning from occurring, but I consider 400 miles extreme. I do it every 1000 miles or so, but I would much rather just watch the gauge and fill it when it is below half. Having the level one of the ScanGauge displays would be great.

604eholston@charter.net · 05-24-2018, 09:31 PM

avanti,
Codes for DEF readout on Scan Gauge 11 on Mercedes, Sprinter 3500:

TXD: 07DF0185
RXF: 032100000000
RXD: 2008
MTH: 006400FF0000
Name: RTL

The readout is in percent of tank filled
Hope this works for you!

Hatteras Jim · 06-09-2018, 02:22 PM

Firm believer (now) of keeping def tank topped off for all the reasons mentioned. I add every 2,000 miles while on a trip and it takes about a gallon each time.

IMO: I would use the supplied fill tube the first time, then dispose of it, and then use a small funnel until your def is gone. The reason being is that the def crystallizes inside of the corrugated fill tube and will be introduced into your tank the next time you add fluid. It is easier to clean a small funnel thoroughly than the fill tube.

I discovered this when I picked up the fill tube the second time and it sounded like a baby rattle. I do not know if the crystals return to a liquid state when re-introduced into the def?

BTW: I store the clean dry funnel in the cabin filter compartment between uses.

Boxster1971 · 06-09-2018, 07:59 PM

Good advice Jim. I also add 2.5 gallons of DEF half way between my 10,000 mile services.

avanti · 06-09-2018, 08:24 PM

Quote:

Originally Posted by Boxster1971

Good advice Jim. I also add 2.5 gallons of DEF half way between my 10,000 mile services.

Yep. That seems to be the right recipe. The trick is guessing when it will take the full 2.5 gallons. I am looking forward to seeing how well the above-described ScanGauge technique works.

Knit · 06-10-2018, 02:06 AM

My Sprinter 3500 Seems to be averaging about 2.5 gallons every 4000 miles. This is mostly highway miles. It’s hard to tell for sure because the Sprinter dealer adds an unknown amount when serviced.

I just programmed my Scanguage II with the codes in this thread and will watch it in the coming months.

Read your MB owners manual. My 2013 manual says to add DEF as needed.

gregmchugh · 06-10-2018, 02:35 AM

Quote:

Originally Posted by Knit

My Sprinter 3500 Seems to be averaging about 2.5 gallons every 4000 miles. This is mostly highway miles. It’s hard to tell for sure because the Sprinter dealer adds an unknown amount when serviced.

I just programmed my Scanguage II with the codes in this thread and will watch it in the coming months.

Read your MB owners manual. My 2013 manual says to add DEF as needed.

My understanding is that a reasonable rule of thumb is that, for a given vehicle, the average DEF usage will be a set percentage of diesel fuel usage. Once you have calibrated your vehicle then you can get a good estimate of how much DEF has been used by tracking how many gallons of diesel fuel you have used since the last DEF fill and multiplying by your calibrated value for the DEF usage as a percentage of diesel fuel.

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