Go Back   iRV2 Forums > MOTORHOME FORUMS > MH-General Discussions & Problems
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 07-15-2016, 03:13 PM   #29
Senior Member
 
Fiesta48's Avatar
 
Fleetwood Owners Club
Freightliner Owners Club
Join Date: Nov 2010
Location: Texas
Posts: 785
15 Discovery

Built in computer readouts are notoriously optimistic to make you think your getting better MPG. Do a actual with paper and pen. They also do not take gen, aqua hot etc usage into consideration.
Gal bought vs miles driven is what matters.
__________________

__________________
Fiesta48 is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 07-15-2016, 07:05 PM   #30
Registered User
 
ChasA's Avatar
 
Join Date: Mar 2007
Location: Apex, NC
Posts: 1,857
Generator or aqua hot have ABSOLUTELY NOTHING to do with MILES per gallon. MPG is how many miles you can go on a gallon of fuel. It is not how many BTUs or watts etc you get from the fuel that is not being fed to the engine.
__________________

__________________
ChasA is offline   Reply With Quote
Old 07-15-2016, 07:12 PM   #31
Senior Member
 
Mr_D's Avatar
 
iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 23,282
46,000 mile average shows 7.6 on the VMS. Running a little below that till it loosens up from the last rebuild.
The VMS units are very accurate and don't /can't measure AquaHot or generator fuel usage.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 CR-V
Mr_D is online now   Reply With Quote
Old 07-15-2016, 07:44 PM   #32
Senior Member
 
SpaceNorman's Avatar
 
Monaco Owners Club
Join Date: Jan 2004
Posts: 832
Quote:
Originally Posted by ChasA View Post
Generator or aqua hot have ABSOLUTELY NOTHING to do with MILES per gallon. MPG is how many miles you can go on a gallon of fuel. It is not how many BTUs or watts etc you get from the fuel that is not being fed to the engine.
Quote:
Originally Posted by Fiesta48
Gal bought vs miles driven is what matters.
Understood - but, when the generator and the aqua hot are pulling the diesel they use from the same fuel tank that feeds the coach motor - it makes calculating the engine MPG statistics a bit more complicated.

According to the information on the Aqua Hot web site ... our Model 400D will burn 1-4 gallons of diesel fuel per day. A Cummin (Onan) QD1000 generator burn .54 gallons per hour at half load - which means a typical 2 hour generator run burns a gallon of diesel.

If you simply divide total miles driven by the number of gallons you stuck in the tank - your results can be skewed pretty significantly. For the sake of discussion let's say you just got home from a 600 mile trip - and it took 75 gallons to refill the tank. The simple Miles/Gallons formula says you got 8 mpg during your trip.

However, it was a 3 day trip ... and you burned 3 gallons per day of diesel to run you Aqua hot (9 gallons for the trip) and ran your generator for two hours each day (1 gallon per day - 3 gallons for the trip) - that's 12 gallons that didn't go to the engine - meaning you actually travelled 600 miles on 63 gallons of fuel - and actually got 9.52 miles per gallon.

In this scenario using the simple Miles / Gallons formula understates your actual engine MPG by 16%. When you're talking MPG that's a pretty significant miss. Let that same 600 mile trip include a 6 day stay where you're burning fuel with the Aqua Hot and the Generator at the same daily rate - and the simple miles / gallon formula becomes more or less meaningless.

If you're trying to track engine MPG - you have to have a mechanism for adjusting for fuel used by your generator and your Aquahot in order to keep the numbers meaningful.
__________________
SpaceNorman
2012 HR Endeavor 43' DFT, 2012 Jeep Liberty
www.penquinhead.com
SpaceNorman is offline   Reply With Quote
Old 07-15-2016, 08:07 PM   #33
Senior Member
 
bruceisla's Avatar
 
Join Date: Oct 2012
Location: Land O Lakes, FL
Posts: 4,139
Quote:
Originally Posted by Fiesta48 View Post
8.95 last trip. Opened up intake and removed full mud flap. Now 9.2. Pulling Accord. Will save thousands $ over next 50k miles.
Newer diesels get better MPG. Includes short idling and gen usage. Cant idle new diesels over 10 min saves fuel. Never in a rush, retired.
I think you'll find your savings is more like $450 over 50000 miles. Not insignificant but not thousands of dollars.
__________________
2005 Newmar Essex 4502
1997 HR Endeavor 37, CAT, 1996 Geo Tracker
bruceisla is offline   Reply With Quote
Old 07-15-2016, 08:14 PM   #34
Senior Member
 
bruceisla's Avatar
 
Join Date: Oct 2012
Location: Land O Lakes, FL
Posts: 4,139
I typically get 6.3 - 7.2 depending on terrain. In California and Oregon with lots of 6% grades and winding roads it was more like 6.3 ... and a bunch of manual control of gear selection.
__________________
2005 Newmar Essex 4502
1997 HR Endeavor 37, CAT, 1996 Geo Tracker
bruceisla is offline   Reply With Quote
Old 07-15-2016, 08:19 PM   #35
Registered User
 
ChasA's Avatar
 
Join Date: Mar 2007
Location: Apex, NC
Posts: 1,857
Right on Norman. The net is that trying to track MPG is futile. Go on down the road and refuel when you need to.
If anyone wants to really accurately track fuel consumption then install flow monitors for everything that consumes fuel or run everything from separate tanks. Then come on here and present some meaningful data.
__________________
ChasA is offline   Reply With Quote
Old 07-15-2016, 08:28 PM   #36
Senior Member
 
Join Date: Feb 2010
Posts: 539
We average 7.5 to 8.1 pulling 3150 lb Chevy HHR
__________________
2008 Thor, Four Winds Mandalay 40G. Cummins 400 isl. Freightliner chassis
koda59 is offline   Reply With Quote
Old 07-15-2016, 08:34 PM   #37
Senior Member
 
Scottybdivin's Avatar


 
Newmar Owners Club
Join Date: Jun 2012
Location: Spicewood Texas (West of Austin)
Posts: 2,746
I recently drove 186 mi, ran my generator for 96 hours straight, with a little Hydro-hot usage, then drove 186 mi home. My fuel mileage was pretty dismal. Burned 114 gal.
__________________
Scotty and Kristen, Airedales Dagny and Wyatt
2007 Newmar Mountain Aire 4528, 450 HP ISM, Allison 4000, 8 Trojan T-105's
2014 F150 4x4 Crew Cab Platinum 157" WB
Roadmaster Blackhawk 2, RVI2 Brake System
Scottybdivin is offline   Reply With Quote
Old 07-15-2016, 09:08 PM   #38
Member
 
jbialy's Avatar
 
Fleetwood Owners Club
Spartan Chassis
Join Date: May 2013
Posts: 46
We have a 382 mile leg tomorrow. I will report back our data.


Sent from my iPhone using iRV2 - RV Forum
__________________
jbialy is offline   Reply With Quote
Old 07-15-2016, 11:00 PM   #39
Senior Member
 
SpaceNorman's Avatar
 
Monaco Owners Club
Join Date: Jan 2004
Posts: 832
Quote:
Originally Posted by ChasA View Post
Right on Norman. The net is that trying to track MPG is futile. Go on down the road and refuel when you need to.
If anyone wants to really accurately track fuel consumption then install flow monitors for everything that consumes fuel or run everything from separate tanks. Then come on here and present some meaningful data.
I'm not sure that trying to track it is futile ... you just have to be cognizant of generator and Aqua Hot use ... and try to factor that in. I try to benchmark engine mileage during trips in warmer months - when I may not be using either the generator or the Aquahot (on diesel). Every now that then I get that 500+ mile run without either the generator or Aquahot running. Those are the MPG calculations that I look at seriously.

I'm a numbers guy by trade ... you just have to understand your sources.
__________________
SpaceNorman
2012 HR Endeavor 43' DFT, 2012 Jeep Liberty
www.penquinhead.com
SpaceNorman is offline   Reply With Quote
Old 07-15-2016, 11:08 PM   #40
Senior Member
 
Mr_D's Avatar
 
iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 23,282
Quote:
Originally Posted by jbialy View Post
We have a 382 mile leg tomorrow. I will report back our data.
You can't figure mileage on that short a trip, you need many thousands of miles to arrive at an average. In fact Cummins says it takes 144,000 miles to establish the correct fuel mileage average. This is from one of their white papers they've published on fuel mileage.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 CR-V
Mr_D is online now   Reply With Quote
Old 07-16-2016, 11:25 AM   #41
Senior Member
 
Country Coach Owners Club
Join Date: Jan 2006
Location: Sacramento Area
Posts: 3,258
Quote:
Originally Posted by Mr_D View Post
You can't figure mileage on that short a trip, you need many thousands of miles to arrive at an average. In fact Cummins says it takes 144,000 miles to establish the correct fuel mileage average. This is from one of their white papers they've published on fuel mileage.
Did Cummins mean Correct fuel mileage or Best fuel mileage.

MPG is MPG, however far you go.

Fuel burned at a dead stop is 0.0 MPG.

Performance wise, we used to think our mpg improved once the diesels hit the magic 30,000 miles break-in point. Not sure we ever proved that in our otherwise busy days.
__________________
Dean
1995 CC Magna #5280
C8.3L 300hp Cummins, 31,000lbs
deandec is offline   Reply With Quote
Old 07-16-2016, 12:30 PM   #42
Community Moderator
 
JMonroe's Avatar


 
Newmar Owners Club
Spartan Chassis
Join Date: Oct 2009
Location: On the road again
Posts: 6,288
I think 7.4 is very good for the size and power of your rig.

I always did my trip planning, when we had the 2010 Revolution - 450hp DEF engine, at 7mpg. Occasionally it would be a bit worse, occasionally a bit better, but over any distance 7 seemed to be where we'd land.

I've only got 2,000 miles on our new coach, Cummins 600hp. Looks like it will be safe to use 7mpg for planning purposes again. We ranged from 6.8 to 7.3 on the various legs of our recent trip. Frankly, I was very pleased to see anything that high on a new engine of that size and power
__________________

__________________
Jay & Peggy Monroe with Dolly
Can't take it with you - don't plan on leaving any behind
2016 Newmar London Aire 4553, Spartan chassis
Wrangler Unlimited toad
JMonroe is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
RV miles per gallon, who wants more? mr mike iRV2.com General Discussion 27 07-20-2015 06:01 PM
Amps per hour? Horsepower per hour? BatteryPro Going Green 5 02-23-2015 07:04 PM
$3.99 per gallon diesel Dennis Lind Country Coach Owners Forum 6 04-28-2008 01:07 PM
Miles Per Gallon ? Alarmguy Class A Motorhome Discussions 44 03-15-2006 02:40 PM
Mile per gallon.....400 Cummins rebelsbeach Winnebago Industries Owner's Forum 14 01-25-2006 03:07 AM

» Virginia Campgrounds

Reviews provided by

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 08:54 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.