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Discussion Starter · #1 ·
I dreamed up this idea the other day that my exhaust wasn't getting hot enough to burn off all that crap that comes out of the engine. I have a 6-speed auto. I started running in fifth gear for the first 15 minutes of driving time at 65mph before letting it go into sixth. The lie-o-meter was reading 18.6-19.2, big improvement from 11-14! I hand calculate every fill up. I always have 13-14. I have run two tanks of fuel through my truck doing my fifth gear for 15 minutes method. Hand calculated both tanks, one was 17.6 and the second was 18.2. I called three different dealers to ask if it hurt to do what Im doing and all three said "no problem". Two of the dealers were from my home state and the other was one that I looked up on the net from Iowa(Had to get a second opinion on these okies:rof)
 

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??? Is this common knowledge? I'd think running in a lower gear would lower exhaust temps.
Should be common knowledge. The 6.7 has been out since 2007 and a half. Most people that didn't lug them around, didn't have troubles. Lower exhaust temp isn't a problem.
 

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Discussion Starter · #8 ·
Hey a fellow okie! (not to far from me either)

Where is a good dealer around here for warranty work anyhow?

Automax in Shawnee is the best so far, and closest. I have used David Stanley once, but you dont get any one on one time to talk with the service guy there. They just shoo you out the door to get you out of their hair.
 

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Im seriously thinking of swapping to 4.10 gears, Im running a 35" tire, comparing my setup to a truck running stock tires with 4.10 gears the 68RFE is within 100 RPM running in 5th gear. Didnt think of it until this thread. I might try it on the freeway, see what I think.
 

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what is realistist overall mpg of 6.7 mega 4x4 3.73 gears?
I'm on my third tank of gas and (hand calculated) have been getting just under 12mpg. Most of that is in-town driving. I'll get some freeway miles later this week and will go through a few tanks..
 

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So, I'm I understanding this right. You only do the 5th gear thing for the first 15 min and then you let it go into 6th or is it good to do that all the time? Is the same true for towing?
 

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The whole object of what ever you do is to keep the RPM up high enough to burn the soot out of the DPF. Towing is not a real issue IMHO as you are usually using more throttle and running with increased DPF temps anyhow. In town 4th gear is just right with my 4.10 rearended dually. On the highway I let it go to 6th. So far in over a year of driving around town, no problems.
 

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if you're putting down the highway below 2000rpm, you might want to kick it down a gear... these aren't 12v's, they are most efficient above 2000rpm
I've already found this out pulling my 13000lb 5er on the interstate at 65mph I get 14mpg in 5th gear and only 12mpg in 6th.:confused013:
 

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The auto will not go into 6th until the temp is up to a pre determined temperature.

I cannot say for towing but i tried driving 60 MPH in 5th gear, my fuel milage went down from running in 6th, Flat ground, empty, no trailer.

in 6th gear doing 60 MPH im turning 1400 RPM.
 

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Running in a lower gear causes the engine RPM to increase and heat up the exhaust components. This also burns more fuel (more firings of the cylinders = more fuel consumption) If doing this for 15 minutes causes burn off of accumulated soot then there would be fewer calls for regen. The question: is the extra fuel consumed during the 15 minutes of higher RPM more or less than the fuel consumed during a regen?
I'd be interested in hearing the results of more owners testing of this theory.
 

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I have a hard time believing this because as soon as you shift to a higher gear the EGTs will begin to drop.
 
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