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Old 10-17-2021, 03:51 PM   #1
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Def for diesel

We are going to buy a DP but do not understand if or when DEF is needed. Please teach a newbie,
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Old 10-17-2021, 03:56 PM   #2
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Hi ! Welcome to IRV2! We're sure glad you joined us!

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Old 10-17-2021, 04:05 PM   #3
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Originally Posted by Walter W View Post
We are going to buy a DP but do not understand if or when DEF is needed. Please teach a newbie,

On modern diesels the DEF is just another tank that you need to keep loaded. You can get DEF at truck stops when you get diesel or just about anywhere (Walmart, any auto parts store, many gas stations, etc.). Depending on your model, you'll use a small amount of DEF compared to the amount of diesel you use. Ours is 2.5%, others are slightly higher or lower. It might sound more troublesome than it is. In reality, you just need to keep an eye on it and don't let it run out. We add a couple of 2.5 gallon jugs when we get to 1/4 tank. I don't like to keep the DEF tank filled. We've gone on many trips where I haven't added any DEF at all. I don't even carry an extra jug with me because it's everywhere. You don't want old DEF. Others will chime in.
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Old 10-17-2021, 04:18 PM   #4
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All DEF is the same, but not all DEF systems are the same.

Beginning in 2010 diesels, DEF is required but the monitoring systems have evolved and there are problematic issues with various years and chassis manufacturers. This is just a note to be sure you investigate the DEF system on whichever coach you consider, based on year of engine and chassis manufacturer. Most difficulties are with 2016 and newer diesels.
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Old 10-17-2021, 04:33 PM   #5
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Welcome to the forum. You should have a guage on the dash as well where you DEF tank is located. We usually do not let it get below 1/4. Best price, but more difficult to fill, is generic DEF at Walmart.

You are joining a good group of friends here with good information to share. Read the various threads here and ask questions as they come up or add information if you can.

Good luck and enjoy the adventure!
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