DEF Question

[Chewelahmike]

I have purchased a Mercedes Benz 2012 Road Trek RS. I am not familiar with the DEF system and have read a lot of negative comment and problems with the DEF system per se. I understand that this year model has NO level indicator except a warning that the DEF is low. Our rig has only 79,000 mile on it. I see the DEF filler cap and have purchased Blue DEF. My question is: Do I fill the DEF fluid up to the fill cap and refill as it drops out of sight in the fill tube?
Thanks in advance.

 

[Porterhouse]

I have purchased a Mercedes Benz 2012 Road Trek RS. I am not familiar with the DEF system and have read a lot of negative comment and problems with the DEF system per se. I understand that this year model has NO level indicator except a warning that the DEF is low. Our rig has only 79,000 mile on it. I see the DEF filler cap and have purchased Blue DEF. My question is: Do I fill the DEF fluid up to the fill cap and refill as it drops out of sight in the fill tube?
Thanks in advance.

I have a MB 3.0 L diesel SUV. There is no DEF gage, which is a little bit annoying. The DEF tank holds 7.5 gallons, which is designed to last until the next oil change every 10,000 miles. If you do run low on DEF, you don't have to worry. You will get plenty of warning messages that will give you some hundreds of miles to get it re-filled. Of course, that doesn't help much if you're on the Alaska Highway with 1000 miles to the next DEF supply store. If you don't refill it, you will keep getting messages telling you how many more miles you have left until the dreaded limp mode. If you go into limp mode you will only be able to go 5 MPH. By the way, this system of punishment is being repealed by the new EPA. You should be able at some point in the near future to get an engine software update that alleviates these DEF problems

 

[Chewelahmike]

Thanks Porterhouse. I had oil change recently. Don't know if the previous owner refilled the DEF every 10,000 miles. Should I wait until I get the message to refill or go ahead now and refill the DEF?

 

[Porterhouse]

Thanks Porterhouse. I had oil change recently. Don't know if the previous owner refilled the DEF every 10,000 miles. Should I wait until I get the message to refill or go ahead now and refill the DEF?

I would just get a 2.5 gal. jug from Walmart for around $10 and fill it up, then just keep what doesn't fit into the tank and use it a few thousand miles later.

Generally, the engine will use 2% to 3% DEF for the amount of diesel fuel it uses, so you can get some idea when to fill.