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12-13-2017, 08:26 AM
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#43
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Senior Member
Join Date: Jun 2014
Location: Buffalo, NY
Posts: 135
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Pretty much always run mine while driving (Onan QD8000). Uses 1/3 of a gallon per hour. I like to keep the house cool while driving.
__________________
Dan
2005 Monaco Diplomat 40 PDQ
8.9L Cummins ISL 400
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12-13-2017, 05:09 PM
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#44
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Senior Member
Join Date: May 2012
Posts: 277
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Quote:
Originally Posted by Ray,IN
Generator use does NOT affect engine fuel mileage, it gets the same mileage whether the generator runs or not. The generator does affect total fuel used when both are running.
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I agree, it would be difficult to get an accurate fuel mileage number if the generator were running for any length oh time. How would you know how much fuel the generator had used.
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12-13-2017, 06:15 PM
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#45
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Senior Member
Winnebago Owners Club
Join Date: Apr 2013
Posts: 1,061
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Negligible.
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12-13-2017, 08:19 PM
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#46
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Senior Member
Join Date: Aug 2017
Posts: 698
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Quote:
Originally Posted by texkayaker
I agree, it would be difficult to get an accurate fuel mileage number if the generator were running for any length oh time....
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Not difficult at all.
Get Silverleaf and you can monitor MPG all the time. It monitors the flow of fuel to the engine, accumulates the miles and calculates MPG. Simple.
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12-13-2017, 08:25 PM
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#47
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Senior Member
Newmar Owners Club Freightliner Owners Club
Join Date: May 2012
Location: Today? Clayton, North Carolina
Posts: 5,093
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Ray, IN is correct. There's a lot of misunderstanding running through this thread. Your engine mpg remains totally unaffected by generator use. What IS affected is your total fuel consumed. To stay accurate you have to separate generator fuel from engine fuel.
We run our 7.5 Onan quite often when traveling. I figure it at .6 gph. I know that my Dutch Star gets 7.4 mpg. At every refuel I note both the generator Hobbs and the odometer. I've created a spreadsheet that accounts for "Generator Fuel Used" and "Net Fuel to Engine". Over 5.5 years it has proven to be quite accurate.
__________________
John and Diane (RIP Lincoln, 21 FEB 22) RVM103 NHSO
Fulltimers since June, 2012
2002 Dutch Star 40, Freightliner, Cat 3126, 2004 Element
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12-14-2017, 09:11 AM
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#48
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Senior Member
Join Date: Aug 2013
Posts: 893
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About 1/4 per gallon of gas per hour if your not using the AC.
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12-14-2017, 09:27 AM
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#49
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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Quote:
Originally Posted by A Traveler
Not difficult at all.
Get Silverleaf and you can monitor MPG all the time. It monitors the flow of fuel to the engine, accumulates the miles and calculates MPG. Simple.
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Yep, my 7.6 mpg over 49,000 miles comes from my VMS 400 CL.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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12-14-2017, 11:58 AM
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#50
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Senior Member
Monaco Owners Club Workhorse Chassis Owner
Join Date: Nov 2009
Posts: 1,363
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change of pace... diesel coaches getting ~8mpg?? lol
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12-14-2017, 01:53 PM
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#51
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Registered User
Join Date: Oct 2016
Posts: 3,026
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Quote:
Originally Posted by WeatherTodd
change of pace... diesel coaches getting ~8mpg?? lol
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What's the funny part, you don't believe it? I'm at 8.3mpg after 37,000 miles with the 8.9L 400hp ISL. I hear it gets better after 50,000.
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12-14-2017, 02:02 PM
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#52
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Senior Member
Join Date: Aug 2017
Posts: 698
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7.5 to 8 mpg is a very real MPG number for the typical DP. About the same for the gassers. Our Mandalay has averaged 7.4 mpg for 97,000 miles.
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12-14-2017, 03:47 PM
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#53
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Registered User
Join Date: Oct 2016
Posts: 3,026
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Quote:
Originally Posted by JFXG
Ray, IN is correct. There's a lot of misunderstanding running through this thread. Your engine mpg remains totally unaffected by generator use. What IS affected is your total fuel consumed. To stay accurate you have to separate generator fuel from engine fuel.
We run our 7.5 Onan quite often when traveling. I figure it at .6 gph. I know that my Dutch Star gets 7.4 mpg. At every refuel I note both the generator Hobbs and the odometer. I've created a spreadsheet that accounts for "Generator Fuel Used" and "Net Fuel to Engine". Over 5.5 years it has proven to be quite accurate.
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Yes, using the generator does not affect the amount of fuel the engine uses to propel the coach down the road. The OP's coach has a diesel engine and diesel generator which are both fueled by the same tank. If the coach travels 64 miles in one hour at 8mpg the engine will have used 8 gallons. With the generator running at 1/2 load, in this case about 30A which would require either both AC units to be on the entire time or 1 AC and the battery charger for the full hour, an additional 1/2 gallon will be consumed. This would effectively reduce the MPG to 7.5 because you will have now used 8.5 gallons while traveling 64 miles.
Tons of variables based on speed, traffic, grade, wind, driving habits, electric load, etc. For this type of coach the "effective MPG" will drop from hardly noticeable to 1MPG, with hardly noticeable being the more common observation.
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12-14-2017, 04:37 PM
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#54
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Registered User
Join Date: Oct 2016
Posts: 3,026
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Quote:
Originally Posted by triplewide
One of the questions in the OP's original post was:
"Just curious to know how much does running the generator while driving effects fuel mileage"
Fuel mileage will be affected if the generator uses the same fuel as the coach. Fuel mileage is affected by amount of fuel consumed, not fuel type, generator size, or brand. Generator efficiency would be a factor if it consumes less fuel per watt generated.
On a 50 mile trip that takes one hour to complete and your generator uses .5 gallons per hour:
If your rig gets 15 mpg with out generator it will get 13 mpg with it.
If your rig gets 5 mpg with out generator it will get 4.76 mpg with it.
If your rig gets 3 mpg with out generator it will get 2.9 mpg with it.
If your generator is only affecting mileage by .1 mpg I would assume it is only consuming about .1 gallons per hour. I am guessing you get better than 3 mpg without the AC(s) running.
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Read my previous post.
The OP owns a 2003 Alpine Coach with 2 roof top AC units, either 13.5K or 15K and an Onan 7.5K diesel generator. I own a 2005. Based on the known fuel consumption rates of our generator and known AC loads in our coach it is possible to estimate the amount of fuel used by the generator and apply that data to determine the total amount of fuel used to travel a certain distance.
Gas coach, gas generator, diesel coach, diesel generator, 4K genset, 20K genset, 17mpg Sprinter, 6mpg Marathon, 80°, 110°, Florida, Colorado, everything will be different.
We get 8mpg, generator sips fuel. Running it while driving is a great way to exercise it if you don't want to run it at a campground or in your driveway or storage after a month long trip where it was never used.
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12-14-2017, 04:39 PM
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#55
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Senior Member
Newmar Owners Club
Join Date: Jun 2012
Location: Spicewood Texas (West of Austin)
Posts: 4,511
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Quote:
Originally Posted by texkayaker
I agree, it would be difficult to get an accurate fuel mileage number if the generator were running for any length oh time. How would you know how much fuel the generator had used.
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You can establish a baseline on the generator if you use it a lot. I once filled up immediately before and after a race event. We used the generator to run all 3 AC's for 96 hours straight. It used 48 gal or 0.5 GPH. That about as close as you can get to any accuracy.
__________________
Scotty and Kristen, Airedales Dagny and Wyatt
2007 Newmar Mountain Aire 4528, 450 HP ISM, Allison 4000, 8 Lifeline AGM's
2019 F250 King Ranch 4x4 Powerstroke - SOLD
2022 F350 DRW King Ranch 4 x 4
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12-14-2017, 04:40 PM
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#56
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Senior Member
Join Date: Aug 2014
Location: Ma.
Posts: 319
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Quote:
Originally Posted by mike brez
We run ours all the time. Has no affect on mpg.
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How can it not affect fuel economy when it’s using fuel from the same tank
__________________
2021 DRV Mobil Suites Elite Columbus 44’ 5th wheel
Thank You
Frank
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