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06-07-2011, 06:17 AM
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#1
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Montana Fan
Join Date: Feb 2010
Location: Calgary
Posts: 351
M.O.C. #10119
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Fuel Economy
While reading an article on a Travel website I found the following information interesting, and I assume this would also pertain to diesel consumption. " While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph (96 km). In fact, according to the US Department of Energy, every five mph that you drive in excess of 60 mph is about the same as paying an additional 24 cents for every gallon of gas".
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DPAM
2017 GMC Denali diesel, crewcab, 4x4, regular box.
2010 Montana 3150RL- Moving to Montana Package , Hickory Edition Package, wet bolts
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06-07-2011, 08:00 AM
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#2
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Montana Master
Join Date: Mar 2010
Location: Land O Lakes
Posts: 2,783
M.O.C. #10246
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The on-board meter in our truck confirms that speed and efficient use of fuel do not mix.
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06-07-2011, 08:31 AM
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#3
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Montana Master
Join Date: Apr 2009
Location: Murrieta
Posts: 5,816
M.O.C. #9257
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In my truck I get the best speed/mileage when I am towing between 61 to 63 mph. Lower than that and I'm constantly downshifting whereby the increased rpms shoot down the mpgs. Higher than that and the mpgs suffer as the rpms and wind resistance increase.
When not towing the sweetspot is about 70-75mph between speeds, rpms and miles traveled.
Since I went over 60,000 miles on my '06 6.0 PSD highway mileage has increased by 1-2 miles per gallon! I'm guessing from what I've read it's about the engine being broken in. I used to get 18+ to 20 and now I get 20+ to 22. With a tailwind I got 26mpg while going 75mph! Unfortunately it seems like no matter what direction I go I get a headwind (why is that?).
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06-07-2011, 09:50 AM
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#4
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Montana Master
Join Date: Feb 2005
Location: Haysville
Posts: 4,261
M.O.C. #3085
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I have the Powerstroke 7.3 with a 6 speed manual tranny and a 4:11 rear end ratio. I get my best milage towing at around 63 mph. When I get above 66 mph towards 70 mph, I loose mpg to the tune of about 2 mpg. Stock fiver tires aren't rated for sustained 70 mph towing anyway.
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06-07-2011, 09:59 AM
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#5
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Montana Master
Join Date: Jan 2005
Location: North Ridgeville
Posts: 20,229
M.O.C. #2839
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We run 62/65 when towing and the MPG at that speed is what it is. I am no expert but as we increase speed our Boost goes up as does our EGT and RPM. I think that means we are using more fuel therefore less MPG .I could be wrong. We do 9.5 to 10.5 depending on conditions and our GCWR is near 23,000 lbs. Our Honda gets 28/30 but it don't weigh near that much.
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06-07-2011, 10:51 AM
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#6
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Montana Master
Join Date: May 2010
Location: Tampa
Posts: 532
M.O.C. #10378
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Just back from a 962 mile round trip towing all but 85 miles. Truck computer said average 11.2, but accurate fuel records and receipts show ave of 9.62. Anyhow, gets down to about $.50 a mile just for fuel, and that was flat land interstate towing at 63 mph.
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06-07-2011, 03:03 PM
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#7
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Montana Fan
Join Date: Aug 2008
Location: Lone Grove
Posts: 147
M.O.C. #8718
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nosticks, I hate to say this but your's may be attributed to the model year of your truck. I traded my 2010 F-350 in on a 2011 F-350 in less than a year because of POOR fuel mileage. I went from about 8 mpg towing with the 2010 to about 10.5 towing my 2955RL. Haven't heard to many good things about the fuel economy of the 2010's.
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06-07-2011, 03:57 PM
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#8
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Montana Fan
Join Date: Mar 2010
Location: Bridgewater
Posts: 389
M.O.C. #10209
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Last year we travelled 25000 KM across Canada, up through the BC interior to the Yukon, then over to Yellowknife and back to the East Coast. Our 2010 PSD 350 dually towing our 2955, combined weight of 21757 pounds gave us 11.8 MPG calculated for the whole trip (not the onboard fantasy numbers). Drove 90 to 95 KPH (about 59 MPH) on good roads and less on bad roads. Got better milage on flat roads with a tail wind, worse milage in the Rocky Mountains and with headwinds. Can't complain with those numbers. Can't think of any truck that is going to do much better. IMO
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06-08-2011, 02:10 AM
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#9
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Montana Master
Join Date: May 2010
Location: Tampa
Posts: 532
M.O.C. #10378
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Maphillips, you are right on the poor fuel for the 2010's. I'll just have to put up with it for a few more years, I own it outright so no payments and interest to look forward to every month, just severe indigestion at the pump.
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06-08-2011, 05:48 AM
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#10
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Montana Master
Join Date: Nov 2003
Location: Santa Fe Springs
Posts: 4,189
M.O.C. #639
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On my 09 Ram/4.11 gears @ 62 mph pulling I will get 11.5 very big hills 10 mpg.
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Pulling a 2004, 2980 RL an oldie but goodie.
Tow vehicle is a 2009 RED RAM 3500 DRW.
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06-08-2011, 08:20 AM
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#11
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Montana Master
Join Date: Oct 2004
Location: Ore City Texas
Posts: 1,648
M.O.C. #2224
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I won't get into the MPG report at this time, but I do keep records based on actual mileage and gallons. This comment is just to say that on our 2007 Duramax/Allison the on-board computer is usually precisely correct. I report this based on the comments that I often read that call into question the accuracy of the computer report.
Incidentally, I still keep that log based on my receipts and odometer. That is the only fully accurate way to determine MPG.
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06-08-2011, 11:08 AM
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#12
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Montana Fan
Join Date: May 2007
Location: Dallas
Posts: 102
M.O.C. #7213
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With our '06 Dodge and 3000RK we have taken four different trips of over 4600 miles each and have always averaged between 11.6 to 12.2 actual MPG, but computer consistantly shows 13.4-14.6. Even last trip through Colorado mountains averaged 11.8 with about 20% of the miles without the Monty. Glad to hear some of you get accurate results from your computer but I definately don't.
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06-08-2011, 12:15 PM
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#13
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Montana Master
Join Date: Jan 2005
Location: North Ridgeville
Posts: 20,229
M.O.C. #2839
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The issue of which is more accurate the Lie O meter or hand calculated... When we check MPH which is not often. We will fill the tank to the very brim. That is one more ounce of fuel and it will spill out. When we refuel we do exactly the same then hand calculate and compare with the Lie O meter. The numbers are always very close. I can squeeze in another 4 gallons of fuel or more after the auto shutoff.
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06-08-2011, 05:14 PM
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#14
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Montana Fan
Join Date: Oct 2009
Location: Pine Island
Posts: 102
M.O.C. #9822
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Next question is do y'all use the odometer reading or a GPS mileage? I know my speedo reads high - maybe 4%, meaning (I think) that my actual miles traveled is that much less.
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06-09-2011, 06:03 AM
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#15
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Montana Fan
Join Date: Apr 2009
Location: Kamloops
Posts: 337
M.O.C. #9238
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Quote:
quote:Originally posted by gypsies2
Last year we travelled 25000 KM across Canada, up through the BC interior to the Yukon, then over to Yellowknife and back to the East Coast. Our 2010 PSD 350 dually towing our 2955, combined weight of 21757 pounds gave us 11.8 MPG calculated for the whole trip (not the onboard fantasy numbers). Drove 90 to 95 KPH (about 59 MPH) on good roads and less on bad roads. Got better milage on flat roads with a tail wind, worse milage in the Rocky Mountains and with headwinds. Can't complain with those numbers. Can't think of any truck that is going to do much better. IMO
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Hi, is your MPG based on the Imperial gallon, or the U.S. gallon?
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06-09-2011, 08:36 AM
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#16
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Montana Master
Join Date: Oct 2004
Location: Salem
Posts: 7,558
M.O.C. #2283
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Greg why don't you check your speedo against the mile markers on the interstate and let us know whit you find over several miles the more the miles the better.
Lynwood
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06-09-2011, 09:12 AM
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#17
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Montana Master
Join Date: Oct 2004
Location: Ore City Texas
Posts: 1,648
M.O.C. #2224
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On a previous pickup I had the tires replaced with a slightly larger size. On I-20 I checked and found that I had about a 3% error. When I reached the 100 mile distance by marker my odometer read 97. I check this several times and found it to be consistent. So after that I made the adjustment before figuring MPG.
Fortunately, my present pickup is on the money!
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06-09-2011, 10:31 AM
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#18
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Montana Fan
Join Date: Mar 2010
Location: Bridgewater
Posts: 389
M.O.C. #10209
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Quote:
quote:Originally posted by Sinterior
Quote:
quote:Originally posted by gypsies2
Last year we travelled 25000 KM across Canada, up through the BC interior to the Yukon, then over to Yellowknife and back to the East Coast. Our 2010 PSD 350 dually towing our 2955, combined weight of 21757 pounds gave us 11.8 MPG calculated for the whole trip (not the onboard fantasy numbers). Drove 90 to 95 KPH (about 59 MPH) on good roads and less on bad roads. Got better milage on flat roads with a tail wind, worse milage in the Rocky Mountains and with headwinds. Can't complain with those numbers. Can't think of any truck that is going to do much better. IMO
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Hi, is your MPG based on the Imperial gallon, or the U.S. gallon?
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Imperial gallon
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