DEF milage and general emissions comments

[Rich W.]

Well I just drove 7714 miles in about 7 weeks (Ca to Austin TX, then Rochester NH, and back to Ca) and got about 323 miles per gallon of DEF. This seems about right to me but it would be nice to compare with the experiences of others.

Also I drove all those miles without any SPN or FMI DTCs, emissions or otherwise - this is a record and unexpected, but greatly appreciated. Never know what’s next with these things, but so far so good. Minor injuries to my knuckles from knocking on wood so much though…

The only thing I did different this time was I always kept the DEF tank full. As soon as it showed it was down 1/4 on the dash I put in another 2.5 gal jug. Also no pump/bulk DEF which is my standard for this rig. I also never hit my 9mpg fuel target but did get 8.9 several times. Low 8’s was much more common, high 6’s to low 7’s in mountain areas.

I did do a little damage elsewhere, had an AC fail ($1800), and my awning came apart (fixed for the cost of a few screws) scratching the paint a bit. Otherwise a fairly easy, but somewhat rushed trip, and I find myself wishing I was still out there somewhere exploring and planning my next stop. Next trip will be a short one out to the coast for some salt air and fresh fish.

Cheers and happy travels!

 

[Neal]

You beat me to it. I'm actually paying attention to this for the first time. I'm trying to get my DEF down to 1 dot so I can get fresh DEF (truck stop is what I use) filled up. I left home in central VA, went to VA Beach, then north to Newmar, then west and am now in Sioux Falls, SD and I'm showing 3 dots so only down 1 dot, I think it's around 1500 miles so far. My hunch is I can make it to Denver but it appears that will be no problem from here. I will probably top off DEF there as I'll be going into the Rockies from there so this test may get cut short. I'll follow up in Denver.

 

[redbaron]

My London Aire is getting 7.7Mpg on Diesel, and 120.8Mpg on Def. This engine is still breaking in as I only have 6200 miles on it.

The def Consumption is about 2x what my ISL engines have been, but the fuel economy is about 1.2mpg more efficient, so I would say it's a fair trade.

 

[redbaron]

BTW, a great free app for tracking fuel, def, and other maintenance is a program called fuelio. I have used this for many years and love the simplicity

 

[RandyB]

Over the last 21,000 miles - 312 MPG DEF

 

[marc2912]

What's the reason behind tracking def mpg?

 

[redbaron]

What's the reason behind tracking def mpg?

For me, establishing a baseline is a key component to early diagnosis of an impending problem.

 

[marc2912]

For me, establishing a baseline is a key component to early diagnosis of an impending problem.

Considering the large amount of miles that each gallon can cover and the size of the tank would it not take considerable amount of driving, 1000s of miles if not more, to notice an issue and then not have much to diagnose off? Maybe I'm just totally missing something here.

 

[Rich W.]

What's the reason behind tracking def mpg?

Your emissions system can leave you stranded when there is nothing else wrong with the vehicle and even when the emissions system is operating properly and only has sensor problems. I’ve had my share of emissions issues and my intent is to a) master and monitor the emissions system on my own, and b) never have to be towed because of it or any other avoidable mechanical issue.

So this trip, at over 7,000 miles in a relatively short amount of time, was a good candidate for observation and establishing a baseline for future reference. I also use box DEF and I like top off the tank at my leisure and convenience and not when Im getting fuel, so I will buy enough for a trip and carry it with me. I can also better control the price I pay this way, having found it at $25 for a 2.5 gallon jug at many locations.

But it was also a matter of simple curiosity. How much DEF does my SCR system use compared to others. Its interesting, although not unexpected, that a 600hp system uses nearly 3X the DEF of a 360hp system. Thank you Redbaron for that info. Also that RandyB’s 6.7 is using about the same amount as mine. All good and useful information.

 

[marc2912]

While I have no clue what my consumption is, this thread did remind me to pick some up. Home Depot $16.28 a box today.

 

[MemoriesByTheMile]

Interesting thread. Have never tracked our DEF economy, but now see the benefit of knowing a baseline and watching for a change.

I also use box DEF and I like top off the tank at my leisure and convenience and not when Im getting fuel, so I will buy enough for a trip and carry it with me. I can also better control the price I pay this way, having found it at $25 for a 2.5 gallon jug at many locations.

Rich, curious about your comment and like to learn. You mention the “convenience and not when I’m getting fuel”, this makes me realize that I am oblivious to something, have a few screws loose or some might say, both.

Wondering about your coach setup and how going to a store on a separate trip to buy DEF and then storing it is more convenient then just grabbing a pump handle for bulk DEF at the truck stop? Only 1.5 years into RVing and still learning.

 

[marc2912]

Interesting thread. Have never tracked our DEF economy, but now see the benefit of knowing a baseline and watching for a change.


Rich, curious about your comment and like to learn. You mention the “convenience and not when I’m getting fuel”, this makes me realize that I am oblivious to something, have a few screws loose or some might say, both.

Wondering about your coach setup and how going to a store on a separate trip to buy DEF and then storing it is more convenient then just grabbing a pump handle for bulk DEF at the truck stop? Only 1.5 years into RVing and still learning.

For me def is a pain at pump since it’s at rear right of my Dutch star, most pumps have def only on driver side so I need to pull fwd and hope the guy before pulled out far enough and then get the pump across somehow and then hope the guy behind understood why I pulled up and am still there. If all that aligns I have to hope the pump allows def after fuel and some do it the other way for some weird ass reason.

 

[Rich W.]

Interesting thread. Have never tracked our DEF economy, but now see the benefit of knowing a baseline and watching for a change.


Rich, curious about your comment and like to learn. You mention the “convenience and not when I’m getting fuel”, this makes me realize that I am oblivious to something, have a few screws loose or some might say, both.

Wondering about your coach setup and how going to a store on a separate trip to buy DEF and then storing it is more convenient then just grabbing a pump handle for bulk DEF at the truck stop? Only 1.5 years into RVing and still learning.

Well yes, pump DEF would be more convenient in some cases if I used it, but I don’t. Also my DEF tank is in the rear on the driver‘s side, and my fuel fills are 30’ away in the front on both sides, and I rarely line up with both a fuel and DEF nozzle at the same time.

I fuel on the passenger side as often as not, and would most often have to move the rig to get a few gallons of DEF. Also I now keep the tank full (to keep my DEF header happy) topping it off in 2.5 gallon increments as soon as the dash gauge reads 3/4, and this usually doesn’t coincide with fuel stops.

I don't use bulk DEF because two of my mechanically disabling DEF related events occured directly after using DEF from a pump. It might have been coincidence, and call it superstition if you want - I wont use it for the coach. I verify date codes and storage conditions before buying DEF, and I test with a refractometer before dumping the stuff into my tank. Lessons learned the hard way dealing with a fragile emissions system. By comparison, my Ford 6.7 can apparently use any DEF without issue, and the DEF and Fuel fills are both in the same location. So it often gets pump DEF.

I can easily carry enough DEF to cross the country and that keeps me from needing to buy it at opportunistically high prices on the road. I like to top off the tank at my liesure in a campground while doing other outside chores, rather than hassle with it while fueling, when there is usually a lot of other stuff going on and truckers waiting for fuel.

 

[Rich W.]

This is one way I dealt with box DEF (and sewer hose) storage:
Before:

After

Three boxes easily fit here. The Active Air valves prevent a forth unfortunately, but on my last trip I carried two more elsewhere. Really made it convenient for me to top off any time, any place I wanted.

Originally I designed this space for “NED“ but I benched him in favor of a mounted tankless compressor, so that made room for DEF.

 

[RandyB]

When using boxed DEF, learn how to read the expiration date codes and speculate on how the product has been stored. Quite a short expiry on DEF.

Blue Def Date Codes

In the continuing game of hiding production dates on BlueDef boxes they changed the date codes again. BlueDef and dealers do not want you to know if you are buying old DEF so they scramble the production date codes. Some time in the last few months it changed again. So far I cannot find a code...

rvforums.com

Additionally do not buy an unsealed box. Reports of customers buying, emptying the DEF, refilling with water and return to the store.

 

[Neal]

I finally decided to add DEF and could have gone much further. I left this trip full DEF and went from Richmond, VA area to Virginia Beach, back to Richmond, VA and north to Newmar. Then west to SD and now in SE Denver area (Aurora) and there is a T/A not far from me so I figured I'd top off diesel and def before my next stop entering the Rockies. I had 2 dots of DEF still showing which is amazing, very efficient. At the tank it was showing 3/8's of a tank remaining. I wanted to get as much of the aged DEF out to fill with new, I've been mixing new/old for 5+ years now.

Added 8 gals which comes out to 300 MPG of DEF