[Archived]

DEF has been a game changer. It is presumed by all involved in regulating its use and those designing the systems that require it that the vehicle with the system is used regularly and that the DEF will be consumed and kept from freezing.

That becomes an issue for those whose use of the coach is seasonal.

DEF has a shelf life and it can freeze which is going to impose a burden on owners. There is not an easy way to deal with it on coaches that are not used regularly and the DEF system is literally a programmed part of the entire engine control system so there is no way to alter the system to reflect its occasional use.

[joel]

What would happen if the DEF aged out? Would we get lower mileage, a CEL or wouldn’t we notice it?

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1999 XLV X-6872,  liberty #440

[Archived]

I have heard the same thing about it going bad, or the quality declining. I guess I will find out next spring since I park for the entire winter here as well. I know that the system monitors the quality of the DEF and will throw a code if it doesn’t like what it sees.

My garage is heated to 60 degrees all winter, so I won’t have the issue of it freezing. This is our first year of ownership of this coach. So far so good. I have had one code dealing with the DEF and it was related to a temperature issue. Prevost told me to just fill the DEF tank and keep going, and it has not happened since. I put on about 20,000 miles this summer.

[Ronald]

We are approaching our 4th year of ownership and 46,500 miles. Early on, I got a check engine light of which the manual said it’s OK to keep driving but have it check at the earliest convenience.

The light went out after 100 miles (happened right after refueling). While getting a regular service at Prevost, they said that there might have been a little DEF that crystalized on the injector. Never happened again.

The coach has been in storage since late March until our current trip to ETLC for service. (Love this resort )

I will fill up our DEF and DIESEL today as the DEF is at 3/4 and the Diesel is just below half. Next trip in about a month.

I do keep both tanks mostly full when not using the coach.

Safe travels,

Mark

[Ronald]

DEF does have a shelf life of one year….That being said with our coaches not putting so many miles on them I would prefer to see the tank low and not full as we tend to do….This will help if we are going on a trip put some in and run it…this would help to run the freshest DEF in the coach and with less in the tank would help in the mixture of adding the new…

The Volvo engine does like to be ran…one issue has been not being ran enough and lines that are part of the exhaust gases, emission can plug up..

[Archived]

Just wondering, for those that have the Volvo engine and DEF, do you note how much DEF that you are using?

I don’t have any hard numbers. We have 55,000 miles now and I’ve noticed lately that we are using less DEF.

Normally, I will refuel diesel at about a half a tank (800 miles) and fill the DEF tank at every ‘other’ diesel refuel as it will start showing ‘half’ a tank of DEF. Our DEF indicator is not super accurate. It will stay on FULL for a long time then start to move.

So, when I go to fill DEF on the second tank of diesel, it would normally show about half a tank. I noticed lately that I’m using less DEF just by looking at the gauge at refill time.

Just wanted to see what others are seeing.

Safe travels!
Mark

[Archived]

Mark

My coach is pre DEF, But I have had a Duramax diesel and currently have a diesel Jeep Grand Cherokee which both use DEF. I have left both vehicle’s in storage for 4-6 months with no problems. I do plan ahead before storing them, I make sure I have Diesel Clean in the fuel tank and I let the DEF get down to around a 1/4 of a tank so when I do start using the vehicle again I add fresh DEF to the tank. Been doing this for quite a few years without any issues. I do live in FL so freezing is not an issue.

[Archived]

My last trip of the year DEF and fuel. I had one more stop that I did not record.

117 gallons fuel, 2.5 gallons DEF

121 gallons fuel 2.5 gallons DEF

169 gallons fuel 4.8 gallons DEF

172 gallons fuel 3.5 gallons DEF

116 gallons fuel 4.2 gallons DEF

So how does that compare to what you are seeing? BTW, my DEF tank gauge is not accurate at all. Hardly moves off of full ever. If I skip filling the DEF tank, it will move down somewhat before the next fill.

[Mark]

That percentage of DEF to gallons of fuel comes out to about 2.5% which is very consistent with the 2% number used by the instructor when I had a class on emissions systems.

I am sure over a greater number of gallons of both fuel and DEF for quite a few more miles a more accurate number will emerge but the ratio the instructor kept repeating was 2 gallons of DEF for every 100 gallons of diesel.

[Archived]

On the last few fuel stops, here are my numbers…

June 22 136.4 gal Diesel

6.8 DEF

Aug 21 148.3 gal Diesel

6.1 DEF

Sept 8 126.1 gal Diesel

No Def refill

Sept. 19 110 gal Diesel

7.8 gal. DEF

Sept. 29 123 gal Diesel

No Def refill

I was going to top-off with Diesel and DEF on OCT. 30th on our way home from NC, but it was raining so hard that I just put it in storage. I’ll pull it out on a nice day for a run for fuel and exercise. I will get both fuels this time. We are going to be parked for a little while.

Mark

[Chuck & Katrina]

That come out to a little over 3%, but I don’t think there is enough information to say that is going to be the number consistently.

But the bottom line is simple. There will be a predictable amount of DEF used per gallon of fuel, and even if it varies a little from coach to coach it is likely going to be consistent over time. That means for those concerned about the life of DEF, protection from freezing, etc. the amount of DEF in the tank on the coach can be run down to a low level so if needed what remains when a coach is stored can be removed and replaced with new fresh DEF when the coach is returned to service.

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2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL