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Old 10-27-2011, 04:04 PM   #44 (permalink)
slowmover
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Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,442

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
Thanks: 1,422
Thanked 733 Times in 554 Posts
As far as avg speed, that's a tough one. When I make my big 800+ mile trip, then yes. I have a gps and can see my moving avg...but around town (and especially when my wife is driving) I do not have an accurate way to gauge it

Just use the "Lie-O-Meter" (overhead console readout) on a per-tank basis: divide miles traveled by elapsed time. This is average mph. When I say I do well with a 27-mph average it generally has little to do with road speed. Obviously, a highway trip will see a higher average. Once one learns how this works in determing fuel use (engine hours versus distance) it keeps one on the straight and narrow. The average falls off drastically with any extended idling.

I would start with the engine hours (see CF for how to find readout as I can't remember right now) and from that determine truck life average mph (as seen in my sig: total miles, total hours, and overall average mph). Make this part of your baseline. (See my signature).

As I recall, Cummins designed these engines with a 10,000-hour lifespan at a 35-mph average. MTBO, or B50 life. Right at 350k miles (unlike GM and FORD where 250k miles is the expectation [I believe the new Ferd finally meets the CTD B50 life design . . we'll see]). A truck with a 20-mph average may not meet that expectation: high hours with low miles, such as a city contractor. And a rancher some ways from town may exceed it with a high mph average per given engine hour. Etc. If 5,000-hours is the putative half-way mark, then I'd need to be at 195,000 miles. No guarantees of "extra" life, but I believe that what we tr to achieve around here is conducive to that end.

Prediction of what the truck can is central, IMO. Solo or loaded. Towing light, or towing heavy. Etc. Many data entry points to figure for accurate predictions. Average mpg & mph figure in for routing choices, terrain, climate and weather anomalies.

I have quite a few posts on CF in re FE. You could do a search under my screen name and the screen name Crabbelle [sp?] in a "post" search; he had a 2nd Gen DRW getting 30-mpg claimed. Pics, mods, etc. I found links to other sites in re his truck and experience. Not a 6.7, granted, but it may lend some insight . . and rebuttal.

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Last edited by slowmover; 10-27-2011 at 04:21 PM..
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