PWernicke

Hi - just got my M Class 350 Blue Tech. I have had diesels for a long time.
I am aware of the ad blue requirement. I trust it is not to difficult to buy a special funnel and fill - slowly and carefully -. In order to never have the
ad blue low warning come on, can I not simply fill it up once a month?

Is it not like diesel fuel in the tank - you fill up in time - lets say by 3/4 empty - and never hit reserve.
It should eliminate the " re-set" warning, failure to start and ever being low.
Correct?

Thank you for any reply.

balticgreen

You can top it off at any time. As far as I know, the warning comes on only when you're low on fluid and not on any sort of time-based schedule, so if you keep it full then you'll never see the warning.

I've heard some people (on MBWorld, no less) say that it's actually better to keep the tank full or mostly full. However, I've also heard that the scheduled maintenance includes completely draining the AdBlue tank every x0,000 miles (I want to say 20k but don't quote me on that), so if you always keep the tank full then there's more to drain, which means more is wasted.

As far as a "special funnel" search around on the forums (or wait for someone to probably post it) but if you buy the refill at the dealership, it comes in a bottle with a special nozzle that fits into the tank in the car. Some people have recommended buying that once, cutting off the bottom of the bottle and then using that part with the nozzle as a funnel. You can find the details on here but it sounded pretty slick and since bottles of the fluid are a lot cheaper at auto stores than at the dealer, you can save money with not much hassle.

Stoneseller

I was told that i should not need to add ad-blue prior to the 10K scheduled service

quinnwhipple

A full add blue system should go 10K+ miles. My 2009 GL Bluetech holds more than 7.5 gallons of blue.

fabbrisd1

THE AdBlue low warning will come on with approximately 2500 miles of driving left - which under normal circumstance will be about 12K miles.

You do not want to overfill - and understand when toppoing off "guggling" or blow back can occur - best "plan" it to buy the MB small botle, use that, then cut off the bottom of the bottle and use that as locking funnel.. Peak 2 1/2 gallon DEF is like $14 at any local parts store

Waykool plantz

I have added @12 gallons in 32000 miles...stared adding at 10k but wouldn't take both 2.5 gal..bout half the second remained.
Haven't seen an add Blu warning yet.

awjenni

There is no harm in adding DEF as you go. I don't know of a simple way to determine how much you have consumed or how much can be added, except by filling until it stops.

I have kept a simple record of my own refills, and it can give you an idea of consumption rates. I purchased the DEF in two 3 gallon plastic jugs (jugs encased in a corrugated box), each with a short hose and filling spout about 10 inches long. A jug cost around $14.00 at Autozone. The quantities with the asterisks are eyeball estimates of the remaining fluid in the jug.

6/23/2012 Delivery of my 2012 Brand new ML350 Bluetech.

9/7/2012 6234 miles - Added approximately 2.1* gallons (filled tank to the top)

12/3/2012 8698 miles - Added .9 gallon (remainder of the first 3 gal. jug, and tank not full to the top)

8/12//2013 13120 miles - Added approximately 2.4* gallons (filled tank to the top)

If you accept the accuracy of my last eyeball estimate, the numbers show a DEF consumption rate of approximately .41 gallons per 1000 miles. That comes to a DEF cost of slightly less than $2.00 per 1000 miles. I can live with that.

Waykool plantz

Your records confirm my experience...thanks for keepin record.

dgiturbo

Imagine how surprised I was to see my new 2013 RAM has a DEF gauge!!! MB are you listening? Wouldn't a gauge on the dash take all the guesswork out of when and how much to top up?
And from what I have seen, DEF usage is tied to fuel consumption. When I tow heavy, I use more than when empty.

So far with 9000 miles on the RAM truck, 4000 miles of that towing heavy, I have used about 10 gallons of DEF. That's about 900 miles per gallon in my case, and I buy the Peak brand where ever I can for about $10 for a 2.5 gallon jug. So about $4 per gallon to go 900 miles on a HD RAM truck.

OP, what I did is buy a blue funnel from a parts store that fit the DEF opening, then when I get to about 1/4 tank, I refill with a 2.5 gallon jug. With my engine being 2X yours, and the mileage I get, compared to awjenni's records, you should have a fair idea of when to top up.