How to Know When to Add DEF

[Bombero71]

Still brand new to the RV life. I have a 2016 Via (diesel). Having never owned a diesel vehicle before, I'm slowly learning the tech stuff. How do I know when I need to add DEF? I bought the RV about a month or so ago and it came with a full fuel tank. The dealer also stated that the DEF tank was full. I've had to fill up the fuel tank once so far, but I don't see any gauges for the DEF. Thanks in advance for helping out a newbie! (I'm in the process of getting the technical and owner's manuals for my RV, but don't have them yet).

 

[P and D]

Here is an AI overview of how to check DEF fluid depending on if you have steering wheels controls or not.
Not sure on Mercedes, but other diesel vehicles we own, when it hits half a tank it will take 2.5 Gallon Jug of DEF.

To check the Diesel Exhaust Fluid (DEF) level on your 2016 Winnebago Via (built on the Mercedes-Benz Sprinter chassis), your method depends on whether your motorhome features steering wheel buttons or dashboard buttons (M and O).Option
1: Dashboards WITH Steering Wheel Buttons (High-Line Display)
If your steering wheel has navigation arrows and buttons, check the level digitally:
Turn the ignition key to Position 2 (On, but engine off).
Press the Home (or folder) button on the left side of the wheel to pull up the main menu.Scroll sideways using the arrows to select the Service menu.
Scroll down to select Additive DEF or AdBlue and press OK.
A bar graph will display the current fluid level.

Option 2: Dashboards WITHOUT Steering Wheel Buttons (Standard Display)
If your steering wheel does not have control buttons, you must use the physical buttons on the left side of the speedometer cluster:
Sit with the engine idling at a standstill.
Locate the M (Menu) and O (Reset) buttons on the left edge of the instrument panel.
Tap the M button multiple times (typically 2 to 3 presses).
It will cycle through remaining service mileage and then flash "DEF Level" or a fluid icon.
The vehicle will temporarily repurpose your dashboard fuel gauge to indicate the DEF level instead of your diesel fuel level.

 

[creativepart]

You Mercedes will alert you when it’s time to add DEF. And when it does you just buy one box (2.5 gal jug inside) at just about anywhere and put the whole thing in. Simple as that. The box includes a flexible pouring spot but beware spilled DEF on your clothes and shoes, it dries bright white.

(FYI: No AI was used in this resonse.)

 

[AlanO-WO]

I would not recommend buying DEF just anywhere. DEF has an expiration date and a shelf life. Stored at higher temperatures shortens the shelf life.
Check the ‘date coding’ stamped on the box for maximum life.
It’s a pain to have to work through the ‘decoding’ process and most don’t make it easy.

 

[creativepart]

If you buy at places that sell a lot of DEF - truck stops, Auto Zone (etc) or Walmart even I doubt you'll find any even close to expiration dates.

 

[Bobn1957]

I would not recommend buying DEF just anywhere. DEF has an expiration date and a shelf life. Stored at higher temperatures shortens the shelf life.
Check the ‘date coding’ stamped on the box for maximum life.
It’s a pain to have to work through the ‘decoding’ process and most don’t make it easy.

I would suck out the old DEF and replace it with new. Bad DEF can cause expensive repairs!

 

[AlanO-WO]

Agreed, I did exactly that when I bought my View. A rather simple job that can save huge problems if overlooked

 

[Retired24]

No need to buy the "premium" def. It's all the same 32% urea and the rest is water. Store it out of direct sunlight and add when it will fit the whole jug. If you have any left over just make sure.to keep the cap on.

 

[Gkiesel]

You will get approx. 700 mpg of def. So 1400 to 2000 miles will use a full box.

 

[PZachary]

Still brand new to the RV life. I have a 2016 Via (diesel). Having never owned a diesel vehicle before, I'm slowly learning the tech stuff. How do I know when I need to add DEF? I bought the RV about a month or so ago and it came with a full fuel tank. The dealer also stated that the DEF tank was full. I've had to fill up the fuel tank once so far, but I don't see any gauges for the DEF. Thanks in advance for helping out a newbie! (I'm in the process of getting the technical and owner's manuals for my RV, but don't have them yet).

I have always def bought a big box stores. I use a syphon hose that you can get from Walmart, or Home Depot. It eliminates spills and is easier to use than the hose that come with the box

 

[wahoonc]

My beast holds 13 gallons of DEF, I have a dash light that tells me how much I have. I use DEF in the 2.5 gallon boxes from WM. I have started using the Rislone DEF additive to minimize the crystalization issue due to heat and lack of use. I also keep the tank topped up. If I think there might be an issue I will suction it out of the tank and put in fresh.

Aaron

 

[Alex Agronick]

I too own a Via, my first time driving distance I lost all power and thought it was the engine. Before dawn in the mountains on I-81 in VA it wouldn’t go past 10 mph. No dashboard warning but it was the DEF. On my Via it’s in an awkward place I can’t dump an entire container without spilling half of it. I use a portable pump. Again, I had NO warning, no dash idiot light.

 

[CapeCodRob-WO]

I would suck out the old DEF and replace it with new. Bad DEF can cause expensive repairs!

How long would you leave DEF in the tank before pumping it out? We've been parked for 5 months without moving. Def system return hose was replaced in MAY at a shop in PA on our trip north to MA due to it leaking. Heading back to FL next month, should I dump the DEF and start fresh?