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Old 08-14-2006, 05:01 PM   #1
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On July 24th we arrived back in Charleston after completing an 8033 mile round trip to and up the west coast. At the end we had 29681 miles on our '03 Winnie. Since joining this forum I have read and taken part in a number of threads dealing with gas mileage for the WCC 8.1 MH's. Being an anal engineer, I was not willing to take what I considered as exaggerated claims of mileage without
documentation. As a counterpoint I have been collecting data on the fuel consumption of my rig since the odometer was reading 5149 miles. The data collected represents a sample of 24532 miles driven over highways in all but five of the lower 48 states, 198 hours of generator usage and towing a '04 Honda CR-V LX for each of those miles. During this period we drove over all types of roadways with greatly varying elevations and environmental conditions. Utilized numerous brands of regular unleaded gasoline with octane ratings from 85 87 (including ethanol mixtures) which we purchased in each of the 43 sates and 4 Canadian provinces as we traveled. Speeds driven ranged from city stop and go to Interstate travel which for limited time periods reached 75 MPH. Over the long haul I would estimate my average highway speed to be around 62 MPH at 2100 RPM. While this is not intended to be presented as a scientific paper, I do hope that it will rise above the level of documentation present in previous threads to justify sustained MPG of 8 MPG or higher. The results are as follows:

Average for the 24532 miles driven 7.20902 MPG

Average for the last 8033 miles driven 7.45772 MPG

Based on this limited sample of one coach, I still think claims of 8.5 or higher are to be taken with a grain of salt. The greatest factor limiting the MPG potential for a motor home is not weight, but is the drag coefficient (Cw) of the frontal area of a coach. For current coaches it is pretty close to 1:1. This with most new cars being nearer to .5 or less. Add to this the engine displacement, operating RPM, GCWR with environmental factors and I challenge anyone to prove sustained MPG in excess of 8 MPG under normal driving conditions. I am an engineer so I take no responsibility for grammatical and/or spelling errors in this posting.
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Old 08-14-2006, 05:01 PM   #2
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On July 24th we arrived back in Charleston after completing an 8033 mile round trip to and up the west coast. At the end we had 29681 miles on our '03 Winnie. Since joining this forum I have read and taken part in a number of threads dealing with gas mileage for the WCC 8.1 MH's. Being an anal engineer, I was not willing to take what I considered as exaggerated claims of mileage without
documentation. As a counterpoint I have been collecting data on the fuel consumption of my rig since the odometer was reading 5149 miles. The data collected represents a sample of 24532 miles driven over highways in all but five of the lower 48 states, 198 hours of generator usage and towing a '04 Honda CR-V LX for each of those miles. During this period we drove over all types of roadways with greatly varying elevations and environmental conditions. Utilized numerous brands of regular unleaded gasoline with octane ratings from 85 87 (including ethanol mixtures) which we purchased in each of the 43 sates and 4 Canadian provinces as we traveled. Speeds driven ranged from city stop and go to Interstate travel which for limited time periods reached 75 MPH. Over the long haul I would estimate my average highway speed to be around 62 MPH at 2100 RPM. While this is not intended to be presented as a scientific paper, I do hope that it will rise above the level of documentation present in previous threads to justify sustained MPG of 8 MPG or higher. The results are as follows:

Average for the 24532 miles driven 7.20902 MPG

Average for the last 8033 miles driven 7.45772 MPG

Based on this limited sample of one coach, I still think claims of 8.5 or higher are to be taken with a grain of salt. The greatest factor limiting the MPG potential for a motor home is not weight, but is the drag coefficient (Cw) of the frontal area of a coach. For current coaches it is pretty close to 1:1. This with most new cars being nearer to .5 or less. Add to this the engine displacement, operating RPM, GCWR with environmental factors and I challenge anyone to prove sustained MPG in excess of 8 MPG under normal driving conditions. I am an engineer so I take no responsibility for grammatical and/or spelling errors in this posting.
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Old 08-14-2006, 05:31 PM   #3
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I have a 2003, 33 foot Brave with the 8.1 L engine, P32 chassis and the 4 speed automatic. I have over 37,000 miles and have been tracking the gas mileage for the last 34000 miles. I tow a PT Cruiser, but do not use the generator alot. I have less than 100 hours on it. My overall average is 7.9 mpg.

I took a trip from Cleveland, Ohio to Alaska on the Winnebago Caravan. The total mileage on the trip was 9900 miles, and the mileage was consistent - 7.9 mpg.

Hope this elps.

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Old 08-14-2006, 05:41 PM   #4
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Don't forget to keep one thing in mind Geeche, many of the claims you might of seen on here can come from a variety of different coaches. Each and every coach can be of different weights and design. As I'm sure you're aware the 8.1 engines are also installed in P-32 and the newer W16 and W18 coaches. The W-20 also is quite a bit lighter. Some of the very light weight coaches are Safari Trek's which are built on W-18 and W-20 chassis'. The mileage can very a lot.

I did the same thing you did with my past coach which was a 2001 Damon Daybreak on the 18,000 lb P-32 with the 8.1 motor. My 20,000 some miles averaged about 8.5 MPG.

I say you are correct based on the typical W-22 chassis. My Fleetwood appears to get very close to what you are saying. Fact is I get at least 1 to 1.5 mpg better when I'm not towing my toad compared to when I am. So weight definitely has something to do with it. Especially in my home state of Colorado.
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Old 08-14-2006, 06:11 PM   #5
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Maybe I'am doing something wrong but my mileage was in the mid 6's on 37' chassis. Kept mpg on trip down to Tenn. filled tank twice and got 6.1& 6.7. Came back same way filled twice mpg had increased to 8.7 & 9.1 on same legs of trip.
Drive with cc most of the time set at 62, 2100 rpm and like I have an egg under foot when cc off.
Have now added wires and sparks and CAI will report back on trip this week as to hows it going, will also keep track of total mileage and gas used as you have on your long trips.
Have 17,560 miles and changed to Mobil 1 and 111 filter around 5,000 miles.
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Old 08-15-2006, 02:45 AM   #6
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The W-20 also is quite a bit lighter. </div></BLOCKQUOTE>
Your reply is good but note that the W20 is not significantly lighter than the W22.
The GVWR is less, but the chassis difference is only tire size, spring rate and rear end ratio and it weighs about the same as the W22. That's what WH customer service told me anyway.
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Old 08-15-2006, 03:04 AM   #7
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Also an engineer and I agree with you.

My 21,924 mile average with rig weighing 20,600 pounds, towing a 3500 pound car over a wide range of terrain and wind conditions is 6.83 mpg. I drive around 63 mph most of the time.

I also keep a moving average - average of last 3 tanks - and it varies from 6.06 to 7.67 mpg.
Head winds seem to make a huge difference.

I have never traveled more than a few miles without the toad so don't know how much that affects the mpg.

BTW I have used 3211.52 gallons of gas. Sure glad most of it cost less than $2 per gallon. Hate to think about the cost of the next 20,000 miles.
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Old 08-15-2006, 11:01 AM   #8
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I are an engineer too.
My spread sheet data for mpg, gen time, gallons, and rolling 1000 mile averages for the last 30k++ miles and 3 1/2 years has been right at 7.1 adjusted for genny use. I also tow a 4000+ liberty better then 90% of the time and loaded at GCW of 26000#.
This data has become the baseline for the Ultrapower tune recently done.

I won't be reporting on this UP adjustment until after several thousand miles of condition averaging to level the field.

Not towing certainly does affect MPG by a considerable amount unless the roadway is verrry level and straight.

Living in the southwest and traveling the northwest mainly doesn't present much opertunity for mostly flat driving. Hill pulling and engine transmission grade braking also don't help[ mileage.

Hoping for better then 7.2 in the next 30 k.
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Old 08-15-2006, 01:26 PM   #9
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I'm getting a hair over 7 mpg 62mph mostly freeway - slow rolling hills of South Dakota and some mountain driving. Towing a Trailblazer.
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Old 08-15-2006, 01:51 PM   #10
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With a 37' Newmar kountry Star pulling Honca CRV LX from Illinois to Montana, I find the two bigest factors impacting fuel consumption are headwind and changes in altitude.
If I tuck in behind a truck doing 62-65 my mileage increases by nearly 1 MPG...and you do not need to be right on top of him to get the benefit.
Of course if you are going up steep grades, the fuel economy goes way down. Going down realy steep grades is not as good as driving in the flat because you need to drop out of overdrive or go down a gear or two to hold down speed.
On my 2000 miles plus in the past 7 weeks, I have ageraged 7.8 MPG. Not bad for overall fuel use given the weight, speeds, and increase in altitude it took to get here.
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Old 08-15-2006, 02:37 PM   #11
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I've kept track of the mileage on my 03 Southwind 32VS since I bought it with 5300 miles on it. I've put about 8,000 miles on her and have averaged 7.33 mpg. I figure with the use of the generator, I'm probably getting around 7.5 mpg +/- About half the total mileage has been towing a Jeep. I typically drive around 60mph. I always check the mpg when I fuel up........I've had a high of just over 9mpg and a low in the 5mpg range. I attribute the differences in filling the tank to different levels, terrain, and wind, but when I take the total miles traveled and divide that by the total gallons purchased, I come up with 7.33mpg........wish I did get that 9, 10 or even 11mpg that I've read about too.
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Old 08-15-2006, 02:51 PM   #12
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by "007":
Maybe I'am doing something wrong but my mileage was in the mid 6's on 37' chassis. Kept mpg on trip down to Tenn. filled tank twice and got 6.1& 6.7. Came back same way filled twice mpg had increased to 8.7 & 9.1 on same legs of trip.
Drive with cc most of the time set at 62, 2100 rpm and like I have an egg under foot when cc off.
Have now added wires and sparks and CAI will report back on trip this week as to hows it going, will also keep track of total mileage and gas used as you have on your long trips.
Have 17,560 miles and changed to Mobil 1 and 111 filter around 5,000 miles. </div></BLOCKQUOTE>

Maybe you were climbing a hill on your trip, and going down hill on your return.
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Old 08-15-2006, 04:25 PM   #13
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Had hills up and down and it wanted to stay in cc in 3d, maybe I have a DP.
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Old 08-15-2006, 05:55 PM   #14
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I haven't adjusted mine for genny use and I use it quite a bit. I suspect if adjusted for it I would be up a couple of tenths of mpg at least.
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