Author Topic: Fuel Mileage  (Read 16360 times)

Keith Moffett

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Fuel Mileage
« on: October 08, 2017, 09:13:40 AM »
We just filled up the tank with diesel.  The interesting thing is that it took only 16.3 gallons.  I literaly tried to squeeze a bit more in but no way.  We had traveled 164 miles from full to fill up.  By my math that says just a tad over 10 mpg. In light traffic on state highways and hilly country.
I would love to figure out what we did right so I can do it again.  Lol
Got to appreciate the good days!
2007 Patriot Thunder
45' C-13
2006 Explorer Ltd.
DW is Carol
Safe travels and
May God bless!

Joel Ashley

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Re: Fuel Mileage
« Reply #1 on: October 08, 2017, 09:50:03 AM »
I was surprised similarly once after a 600 mile jaunt, and calculated 10mpg.  It was all freeway, and cruise set at 60 to keep it from slipping down to 5th gear.  But on reflection and weather check, I realized the wind was at our back virtually the entire way.  I've since been more attuned to wind direction on trips, and conclude it has more effect on mileage than most of us think.  On subsequent drives along the same route I've not posted such good numbers;  there were more head-on and side winds.

Joel
Joel and Lee Rae Ashley
Clackamas, Oregon
36.9 ft. 2006 Monterey Ventura IV, aka"Monty Rae"
C9 400HP Cat

Jerry Carr

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Re: Fuel Mileage
« Reply #2 on: October 08, 2017, 01:38:23 PM »
Keith it must have been down hill, in 9 year with our C13 I would see brief times of 8mpg but when I check the trip log on the Aladdin  it's always 6 bummer
Regards,
Jerry Carr
Past Region 1 V.P.
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Steve Huber Co-Admin

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Re: Fuel Mileage
« Reply #3 on: October 08, 2017, 01:51:52 PM »
Wind can raise havoc with fuel consumption. Yesterday I only averaged about 6-7 in my Jeep Liberty towing a small trailer and fighting a strong headwind all day.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Dave Atherton

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Re: Fuel Mileage
« Reply #4 on: October 08, 2017, 04:56:04 PM »
Gentleman, fuel milage ( what is that ) ?? Your engine ECM holds that information along
with engine rpm and miles. In most cases milage Cat 3126 to C-9, 7 - 8 mpg. Cat C-12
10 mpg, Cat C-13 - C-15  5 - 7 mpg. This is information extracted from engine ECM for
many members with Cat ET computer readout and printout. The Cat C-12 hold constant
10 mpg. There are many areas will reduce milage, wind, speed, load, tire size etc.
Dave Atherton Retired Cat Mechanic

Gerald Farris

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Re: Fuel Mileage
« Reply #5 on: October 08, 2017, 05:40:00 PM »
Keith,
There is a factor that you probably did not consider, how level was the coach from side to side when filling on the last two fuel stops. With the fuel tank location on your coach (side to side), you can use the leveling system to raise one side of the coach and add as much as another 20 gallons to a previously full tank. Therefore, if the coach was not identically positioned, your short distance test was meaningless.

To test fuel economy by the amount of fuel pumped, you need to test several tanks of fuel with the coach perfectly leveled at fueling, and accurately track the amount of fuel used by the Onan and AquaHot. The most accurate fuel mileage that is available to anyone that does not obsessively track consumption in this manner is available by reading mileage from your Aladdin/Silverleaf system. Anything else has too many variables that make an accurate or even a close calculation impossible.

Gerald
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David T. Richelderfer

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Re: Fuel Mileage
« Reply #6 on: October 09, 2017, 01:01:37 AM »
We get about 5 mpg and that includes usage through the generator and AquaHot.  I keep a log of location, miles driven, gallons to fill, and fuel cost per gallon at every fill-up.  The lowest I have seen in five years was 3.8 mpg, the highest was 6.3 mpg.  I do not keep track of the hours of usage by either the generator or AquaHot between fill-ups.  Downhill makes a huge difference, obviously.  And traveling at 62 mph instead of 68 mph seems to make a substantial difference as well.

I usually try to tilt the coach away from the fuel pump when I fill the tank.  That seems to help not only the fuel flow down the tube into the tank, but also helps get the tank filled closer to full.

My brother has a 2000 Beaver Marquis Tourmaline with the C-12, 425 hp engine.  He gets 8-ish or better mpg and tows his pickup.
2004 Beaver Marquis Sapphire

I had a dream... then I lived it!

Steve Huber Co-Admin

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Re: Fuel Mileage
« Reply #7 on: October 09, 2017, 03:26:04 AM »
My Aladdin Jr gives fuel used by engine so my assumption is that it should be fairly accurate.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Bill Sprague

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Re: Fuel Mileage
« Reply #8 on: October 09, 2017, 12:49:50 PM »
Keith,

On "economy days" I would set the cruise to 55.  The Alison would rest in fifth.  With a tail wind on a flat interstate I would see as high as 11 when the 12 year average on the Cummins was 8.3. 

Bill

LaMonte Monnell

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Re: Fuel Mileage
« Reply #9 on: October 09, 2017, 02:55:24 PM »
On my Contessa I see about 7.5 mpg continuously with the 3126B CAT. And thats towing my SRX. I don't really pay much attention as we used to have a large boat and cried at the pumps a few times.
Lamonte & Patti Monnell
2001 Beaver Contessa Naples DP 40' 2 slides
CAT 3126B
2021 Chevrolet Silverado Trail Boss

Weeki Wachee,Fl

Bob Bulot

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Re: Fuel Mileage
« Reply #10 on: October 09, 2017, 04:19:03 PM »
 My similar ‘06 Marquis/C13 hasn’t hit 7mpg yet, even on straight level flat ground.

One interesting observation on the road this summer for the first time with the Marquis:  Increasing my speed from 60 MPH to 65 MPH on cruise control did not result in any reduction in fuel consumption.  I think that this is because the “Sweet Spot” for the C-13 is around 1650 rpm, and 65 mph puts me pretty close to that engine speed. 

Just a couple of other observations:

For a 45’ coach weighing north of 50,000 lbs, full of liquids and Doritos, with a C13 Cat to average 10 mpg on relatively level ground, under almost any conditions is almost impossible.  This raises the probability that some undiscovered variable was in operation.  I have gotten wildly varying figures when I thought I had filled the tank, but failed to notice that the coach was leaning toward the fill spout, for instance.

My Alladin system is consistently inconsistent in its read outs, for another.  It is currently showing a 5-7% lower odometer reading (compared to my GPS). 

Also as previously mentioned, a strong tailwind can also provide surprising increases in mpg figures.

My previous coach was a 40’ MONACO Windsor with a 370 horse Cummins.  It was more than 10,000 lbs lighter than the Marquis.  Without a tow car attached, I could achieve a consistent 10mpg.

Keith Moffett

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Re: Fuel Mileage
« Reply #11 on: October 10, 2017, 01:17:48 AM »
Good points all.  I have had the experience were we were on a slanted pad while filling.  This was not the case in this instance nor was there a good tail wind.  I did fail to mention that there was a moderate amount of time at idle  for repairs etc.  At no time were we in economy mode on the shifter.  Perhaps I am dreaming but it is a nice dream just the same.  Lol
2007 Patriot Thunder
45' C-13
2006 Explorer Ltd.
DW is Carol
Safe travels and
May God bless!

Joel Ashley

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Re: Fuel Mileage
« Reply #12 on: October 10, 2017, 04:18:15 AM »
Bob, although some have modified their tranny's factory programming, it's common for the Allison to shift up to 6th at about 62 or 63mph.  It'll stay there until the speed falls to 57.  So at 60 you were likely in 5th, and in 6th at 65.  The higher speed would have used more fuel had it stayed in 5th, so the cruise in 6th at lower rpm probably compensated, providing comparable mileage. 

Where possible, my practice on open highway is to speed up into 6th, then let it slide back to 59-60mph, maintain that, and try not to let it slip on a slight incline back toward the 57 mph downshift.  The cruise control is steadier than my foot also.

Joel
Joel and Lee Rae Ashley
Clackamas, Oregon
36.9 ft. 2006 Monterey Ventura IV, aka"Monty Rae"
C9 400HP Cat

Bob Bulot

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Re: Fuel Mileage
« Reply #13 on: October 10, 2017, 05:14:43 AM »
That’s exactly what I do. Joel.  I make sure I’m in sixth and then set the cruise.  The Vorad out votes me sometimes if I tuck in behind a slow truck.

In California, I can’t go 65 in many places, and even though I’m actually more relaxed at 60, its nice to be able to step it up a little without worrying about burning extra fuel when happy hour is calling and you still have a ways to go.🍷🍷🍷

Fred Cook

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Re: Fuel Mileage
« Reply #14 on: October 10, 2017, 01:03:42 PM »
Gentleman, fuel milage ( what is that ) ?? Your engine ECM holds that information along
with engine rpm and miles. In most cases milage Cat 3126 to C-9, 7 - 8 mpg. Cat C-12
10 mpg, Cat C-13 - C-15  5 - 7 mpg. This is information extracted from engine ECM for
many members with Cat ET computer readout and printout. The Cat C-12 hold constant
10 mpg. There are many areas will reduce milage, wind, speed, load, tire size etc.
Dave Atherton Retired Cat Mechanic

Is this right.... C-12 gets 10 MPG?  Also will an additive make a difference?
Fred & Cindy
2002 Beaver Patriot Thunder 455, C12 CAT
Towing 2019 Chevy Equinox, AWD Diesel
South Central Missouri, US Army Retired