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.