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Old 01-22-2015, 08:53 PM   #1
Tom and Phyllis
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Usage rate for DEF

I have finally located a site than attempts to predict how much DEF an engine will use.

Default dosage rate is 3% DEF per every gallon of diesel fuel based on engine manufactures suggestion.

This is the website. Hope it helps, so we can carry enough of the stuff with us.
Diesel Exhaust Fluid - DEF - DEF Usage Calculator

On their web site put in the distance and the average mpg and it will figure the amount you will need based on 3% rate of infusion. If you can find out if your engine uses a different rate you can change the 3% to whatever.
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Old 01-22-2015, 08:55 PM   #2
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Why do you want to carry more than maybe 2.5/gl carton?
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Old 01-22-2015, 08:59 PM   #3
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Since the stuff is available everywhere, I don't know why you would want to be caryring extra.
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Old 01-22-2015, 09:11 PM   #4
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The DEF tank holds plenty...for any trips... we can find it in most places... If headed to the deep dark area, load up..

When Warranty expires, it would be a shame if the def stuff fell off on the road somewhere..
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Old 01-22-2015, 09:26 PM   #5
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Originally Posted by slowmover View Post
Why do you want to carry more than maybe 2.5/gl carton?

Good strategy. I fear the engine shut down mode but one small jug would hold you over a few hundred miles...

I can never tell how long it's going to last. When I'm towing it seems to use more. I filled it up the end of the summer and it still says it's "ok" (really wish it gave a %age remaining...).
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Old 01-22-2015, 10:00 PM   #6
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3% rate is double my usage rate. Probably accurate for a semi.
GMC 2500 Duramax has been running right at 1 gal per 1,000 miles.
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Old 01-23-2015, 09:45 AM   #7
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Did an 8500 mile trip last summer, did replenish the DEF tank a few times (RAM has a gauge like the fuel gauge, so not hard to know when to refill). Usage rate varied based on terrain. Going through the Rockies used more DEF (and diesel!) than the flatlands. It is available just about everywhere -- if they sell diesel fuel they have DEF (my experience anyway). You can also get it -- sometimes on special -- at AutoZone or Walmart. Not a big deal.
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Old 01-23-2015, 10:09 AM   #8
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Ford 6.7 averages 13.7 MPG towing 30' AS and uses less than a gallon of DEF every 1,000 miles. I carry 2.5 Gallons just in case, more camping neighbors have used it than I have.

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Old 01-23-2015, 11:19 AM   #9
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I am averaging 1200 miles to the gallon. It is readily available at truck stops, many at the pump, any auto parts store, sam's club and walmart. It has a shelf life of 2 years or less depending on storage temperatures.
When i got the 13 Ram I bought a 2.5 gallon jug and carried it around for over 6 months so now I buy as needed.
If you do a Google search you can find out how to read the date code on the Peak Blue Def boxes which seems to be the most common brand
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Old 01-23-2015, 01:43 PM   #10
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Def for Sprinter

We tow with a 2013 3500 Sprinter that has a 5 gal DEF tank. We get almost exactly 10K miles out of the tank--2,000 miles/gallon of DEF. The Sprinter allows 16 starts after the warning, and because the DEF is so wildly available--autoparts stores, and every truck fueling spot--we've ceased to worry about it!
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Old 01-23-2015, 01:53 PM   #11
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DEF usage is a function of fuel usage. As such, miles per gallon of DEF isn't accurate for comparison. Gallons of fuel per gallon of DEF is the correct "gauge". Anything that causes fuel mileage variation will distort a miles per gallon of DEF analysis. Idling, towing, solo, mountains, wind.....etc.

There's really no need to carry any. On GMs, a readout comes on at 1000 miles left, 600 miles left, 200 miles left....and a couple others as you are about to run out. (I've never run it below 200 miles left message. I think the messages are explained in the owner manual.

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Old 01-23-2015, 02:03 PM   #12
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I have a 2011 Chevrolet 3500 Duramax with 80,000 miles on it. I have been averaging 1,000 miles per gallon of DEF used. I keep a log on when I last added DEF. I have found the DEF warning feature on the vehicle to be completely unreliable. My driver information center indicator has been showing that I have a 460 mile DEF range for the last 30,000 miles. It has been to three different dealers and none have been able to correct it.

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Old 01-23-2015, 02:06 PM   #13
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will PM you, Brian.

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Old 01-23-2015, 07:51 PM   #14
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My 15 Silverado 2500 duramax has 17000 miles on it mostly towing. When I'm doing 14-1700 mile tows I pick up a carton at Walmart and usually add it on the road somewhere when refueling. When it gives me a percent left I add the 2.5 gallons as the percent seems to go down more quickly than I would expect. Otherwise I never carry DEF with me. Always check the date code.
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