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Old 03-24-2014, 02:03 PM   #1
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The Secrets of Better Fuel Economy

Here is a Brochure by Cummins on the subject of Fuel Economy. Although it is directed toward Highway Trucks, there is some interesting reading for RV drivers also. Good bedtime reading.
This is what happens when a person has too much time on their hands searching the Internet.

What caught my eye was the part on Lubricants and comments about Synthetic Lubricants.
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Old 03-24-2014, 06:56 PM   #2
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Thanks for the brochure.
Jim and Lynda, (Sophie, Jake, attack trained killer Shi-Tzus :-))

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Old 03-24-2014, 09:05 PM   #3
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drive more downhill
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Old 03-24-2014, 09:07 PM   #4
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Great info. Thanks!
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Old 03-24-2014, 09:14 PM   #5
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35,000 to 50,000 for tires to break in, wow.
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Old 03-25-2014, 05:21 AM   #6
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I also see the mpg changes with speed. When I set my cruise at 62, on the flats I get about 6.5 mpg, at 70 it drops to 5.5 to 6.0 mpg.

I did not realize the differences tires make at lower speeds. I guess I'm glad my tires are 3 to 4 years old, LOL! Tire pressures are important, for both mpg and load bearing.

Very eye opening report.
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Old 03-25-2014, 05:56 AM   #7
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The part of the report that talks about ideal grading and operating RPM is particularly useful for the motorhome crowd, although we (as a group) cant configure the motorhome for ideal grading. For ideal operating RPM however, we can control that to some extent by choosing speed.

Toterhome with 80,000 GCWR, usually 65,000 as it rolls down the road.
At 62mph on the interstate: 7.4
At 65mph on the interstate: 7.8
At 68mph on the interstate: 7.6

Verified over a few thousand miles to equalize ambient conditions. The difference? It will not hold 12th gear (highest OD) at 62mph because its below peak torque/boost, which results in a drop to 11th gear. Sometimes 10th. At 65mph, while the drag is more, the time in highest gear is more.
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Old 03-25-2014, 07:14 AM   #8
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I found the very last item in the report to be interesting. Appendix C, which shows the "first fill" data. Is this saying that mpg is affected by "break-in" factors way up into the 100,000 to 140,000 mile range? If so, it seems to be a much greater factor on mpg than any of the previously mentioned items.
Maybe I misunderstand Appendix C.
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Old 03-25-2014, 08:47 AM   #9
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I get crummy milage! I gotta read this
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Old 03-25-2014, 09:01 AM   #10
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Originally Posted by dons2346 View Post
35,000 to 50,000 for tires to break in, wow.
Someone should tell that to Goodyear. My Goodyears were shot by 40,000.

Here is my promise to Goodyear: I will never again buy another Goodyear tire - ever.

The biggest factor for us is wind. Wind right on the nose is a mpg killer. Wind on the nose versus wind from the rear can make a difference as big as 4 mpg.
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Old 03-25-2014, 09:02 AM   #11
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An interesting read, thanks Dennis.
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Old 03-25-2014, 02:43 PM   #12
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Originally Posted by danes-on-tour View Post
...The biggest factor for us is wind. Wind right on the nose is a mpg killer. Wind on the nose versus wind from the rear can make a difference as big as 4 mpg.
Agree, along with speed...they are the two biggest detriments to ''good'' mileage.
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Old 03-25-2014, 02:47 PM   #13
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Originally Posted by dons2346 View Post
35,000 to 50,000 for tires to break in, wow.
Yeah, just as they are getting hard & cracked for most of us, they start getting better mileage. It figures.
Larry & Cheryl Oscar, Louie, Ranger & Henry (our Springers)
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Old 03-25-2014, 08:42 PM   #14
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Thank you Dennis. I too found the part about synthetic oils enlightening. That is proof enough for me to not uselessly spend money on synthetic motor oil.
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