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Old 06-21-2012, 04:26 PM   #29
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Originally Posted by richardcoxid View Post

According to your previous post the cost of DEF add about $0.001 to the cost of a gallon of Diesel. If my mental gymnastics is correct, you are saying that ONE THOUSANDTH of a dollar which is ONE TENTH of a cent added to the cost of a gallon of Diesel. Am I misplacing a decimal point or zero?
As best I can tell, I'm getting about 3,000 miles out of every 2.5 gallon jug of DEF under mostly towing conditions. For me, that works out to around $0.0036 per mile. As far as mileage is concerned, we pull about 16,500 lbs. With our '03 F350 7.3PSD we we getting around 9.5mpg. From our '08 F450 6.4PSD we were averaging 8.4mpg. Now with our current truck, we're averaging around 10.3mpg. Way better mileage than the '08, and a little better than the '03. I'm told that less towing reduces the demand on the DEF which could get the cost even lower.

Overall, using DEF is a non-issue for me. It's easy to refill, it's readily available, and if I forget to check the tank reading, I get a display reminder about 800 miles ahead of any performance reduction.

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Old 06-22-2012, 02:52 PM   #30
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this is very educational and well worth reading.
Attached Files
File Type: pdf myths.pdf (92.8 KB, 32 views)

Tony & Yolanda / Katie & Spencer (the Doodles)
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Old 06-22-2012, 03:59 PM   #31
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Originally Posted by JMonroe View Post
I've found the Cummins estimate of 2% DEF usage to diesel to be pretty accurate. In fact, I'm using a bit less DEF than that estimate. At 8 mpg and $4 per gallon of fuel you'd be using about $200 of fuel to go 400 miles. Purchased in 2.5 gallon jugs you can easily find DEF at under $12 for that jug, or about $4.80 per gallon. You're adding just under 10 cents per gallon of fuel at these conservative numbers, or just over one cent per mile.
And I think if you get it from a pump at a truck stop, it's about half that.

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Old 06-22-2012, 04:46 PM   #32
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Just bought 4 jugs today at Napa today. Sale... price was $9.99
per 2.5 gal jug or thats $3.99 per gal.
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Old 06-22-2012, 04:48 PM   #33
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As far as effect on MPG, my engine has never gone into the regeneration cycle in over 18K miles. I have a smaller engine (6.7 L) pulling 30K pounds (with toad) and almost always travel at 55-65MPH on major highways. It seems that the computer monitor is programmed so that this type of driving is considered to regen itself - possibly by guaging how much of the time the temperature of the DPF is above a certain threshhold.

Excerpt from Wikipedia:

" Typically a computer monitors one or more sensors that measure back pressure and/or temperature, and based on pre-programmed set points the computer makes decisions on when to activate the regeneration cycle. "
2008 Itasca Meridian 37H & 2015 Flagstaff T12RBST
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Old 06-22-2012, 05:33 PM   #34
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Originally Posted by Coached View Post
this is very educational and well worth reading.
Hmmm ... actually is so ironic it's almost funny, given Navistar's current massive problems. They still haven't gotten certification, and are running out of credits to use so they could continue to sell non-compliant engines. The Wall Street sharks are circling ...
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Old 06-22-2012, 05:47 PM   #35
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Originally Posted by mhs4771 View Post
K-Star, you're a little off base with your reply. DEF and DPF are two different systems, but the newer trucks generally have both (I'm only sure about GM). DEF is internally mixed with Fuel (at a predetermined rate based on fuel flow) to allow the SCR to reduce the NOX level. The DPF still traps soot particles and now instead of flooding the engine with raw fuel, fuel is injected directly into the DPF where the temps are high enough to ignite the fuel and burn off the soot, called the Regen Process.
OK, I'm no gearhead, but this isn't how Cummins explains it. My understanding is that the DEF is injected directly into the exhaust stream, where it combines with NOx, releasing nitrogen and water vapor. I don't see mixing DEF with fuel anywhere in their explanation.

But hey, I'm owning my ignorance here -- if I'm wrong, somebody please 'splain it to me.

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