Fuel mileage reduction when towing

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sp

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raleigh north carolina
Greetings to all,

We are new to Class A's.  Last fall we purchased a 2009 Winnebago Journey, which is 35 feet, weighs +/- 33,000 pounds with a 350 HP Cummings and 6 speed Allison.  The original owner indicated fuel mileage would be 10 MPG, which was hard to believe; however, on the 900 mile return trip home after the purchase we indeed got +10 MPG.  Then on a trip to FLA in late winter while towing a toad (Subaru Forester +/- 3,300 pounds, manual transmission in neutral and no toad brake dragging ) we only got 8 MPG.  I was surprised that the MPG dropped this much (20%). Is this amount of drop in MPG normal or excessive?

Thanks for any input,

Bob Schultz
 

Kim (skyking4ar2) Bertram

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Bob,

One trip is probably not enough to fuss over because of all the different factors, perfectly full tank or not, road conditions, traffic stop and starts, and personal driving habits.

Having watched a 300hp 38' MH pull a 3250# Honda from 5.9 to 8.9 and a 450hp 42' MH pull the same car at 7.5 to 9.2, it's really hard to extrapolate. We get great mileage at one speed flat, and drastically reduced mileage in the mountains.

Over time, though, you get a better sense of what the overall mileage should look like. Everybody brags about the one trip that got 10mpg but nobody talks about the one that was 6mpg.

It's the price we pay to have fun!

Kim

p.s. reading your post more closely, it appears one trip was towing and one not. In that case, I don't think the drop was excessive at all. Our coach was delivered to us empty in Utah at 10mpg. It has never seen that since, but does often hit 9mpg towing in the flatlands at a constant 62mph.
 

Larry N.

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sp said:
Greetings to all,

... however, on the 900 mile return trip home after the purchase we indeed got +10 MPG.  Then on a trip to FLA in late winter while towing a toad (Subaru Forester +/- 3,300 pounds, manual transmission in neutral and no toad brake dragging ) we only got 8 MPG.  I was surprised that the MPG dropped this much (20%). Is this amount of drop in MPG normal or excessive?

Thanks for any input,

Bob Schultz

That's not out of line, Bob. After all, you're adding a ton and a have to move along, plus a lot more drag (air and road resistance). But, as Kim says, you really have to check mileage over time, looking for an average, since wind, terrain, altitude, speed, steadiness of your foot or cruise control and even road surface can all change your mpg to some degree.
 

Gary RV_Wizard

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I think a 20% hit is unreasonably high if we are talking about towing a car behind a motorhome, but there are many variables. Gas chassis coaches, especially Class C's, often report about a 0.5 mpg hit when towing, but that's more like 5% than 20%. Larger diesel coaches usually see little or no appreciable difference, probably because the towed car is a proportionally smaller effect on the larger and heavier rig.

Weight is not much of a factor on level roads - just a small increase in the rolling resistance from 4 additional tires on the road. Climbing grades, however, means every pound is extra load to drag to the top of the hill (and to brake on the way gown, too). You might see a substantial hit in hilly terrain.

Depending on the specific coach and towed car/trailer, you may also see a hit from increased wind resistance. Certainly towing a largish box trailer is gonna make some difference.

You can't make any solid judgements on just a couple tanks of fuel.  MPG can vary a lot because of the variables, so you have to average it out over a longer period to gain a good understanding. And 8-10 mpg is probably the range of difference you should expect due to differences in terrain, traffic, speed, weather, etc. And now you will also encounter bio-diesel blends at some pumps, and get lower mpg because the energy content per gallon is 5-10% lower.
 

Kevin Means

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As a frame of reference... over a one year period time, we've seen a .5 MPG increase in fuel burn when we're towing my wife's 5000 lb Acura vs. not towing it. That's at 65 MPH with the cruise control on as much as possible.

Kev
 

WILDEBILL308

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I have never made a trip not towing so I have no idea what my mileage might be not towing. I am getting 9+ towing my 2014 CR-V. I think if you average your mileage over 10 tanks you will get a realistic average. I do think a drop 2mpg would be excessive.  I have had trips that really hurt my overall mileage. I have had it drop to 6.5 at different points on a trip. I would not be overly concerned with your mileage at this time.
Bill
 

Arch Hoagland

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Over 80,000 miles I have averaged 7.1 mpg pulling a 4,000lb toad.

I recently did a 1,200 miles trip without the toad and averaged 8.1 mpg.

So, for me, I calculate it costs me about 1 mpg.

However I'm getting two vehicles there for the same amount of fuel some I figure I'm actually averaging 14.2 mpg.

Gonna start towing two toads to bump my mpg to 21.3 mpg.
 

Larry N.

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I think a 20% hit is unreasonably high if we are talking about towing a car behind a motorhome, but there are many variables. Gas chassis coaches, especially Class C's, often report about a 0.5 mpg hit when towing, but that's more like 5% than 20%. Larger diesel coaches usually see little or no appreciable difference, probably because the towed car is a proportionally smaller effect on the larger and heavier rig.

In flat country I'd agree with you, Gary. But in the western mountain regions, you get lots more penalty for going up the hills with the extra weight but don't gain a corresponding amount on the downhill swing. Of course I always have headwinds, too.  ;D
 

Kim (skyking4ar2) Bertram

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Larry,

My experience is more in line with yours, especially since we tend to be at elevation most of the time. That's why 2 mpg did not shock me because my experience is 1 to 1.5 easy. Flat is way different.

Folks can draw their own conclusions, but there is no way to guarantee any MPG number; they get what they get when you drive 'em... 8)

Kim

p.s. I find the response "if you have to ask, you can't afford it" a little too salty for my taste - you can ask all you want to get some kind of range and then plan to move other expenses to catch the highs and lows...over a year's time, using an 8,000 mile average usage, at $2.50 a gallon diesel, the difference between 8 mpg and 10 mpg is $500. Divided by 12, that's ~$42 per month. I can skip a Mexican dinner with Christi in Santa Fe once a month and get that back.

Figures lie and liars figure...  8) Just sayin'...please deduct my two cents from that dollar you owe me.  ;)
 

WILDEBILL308

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Larry N. said:
In flat country I'd agree with you, Gary. But in the western mountain regions, you get lots more penalty for going up the hills with the extra weight but don't gain a corresponding amount on the downhill swing. Of course I always have headwinds, too.  ;D
Well I didn't find that to be true with my coach. Last summer I did a trip west for 75 days and over 12,000 miles. My worst mileage was in California where I had to drive 55 because I was towing. mileage for last year was 9.3 mpg.
Why am I always driving up hill into the wind?
Bill
 

sp

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Thanks for all the informative feedback.  I'll check the mileage over the next several trips.  I realize that road conditions will affect mileage and maybe that was the case on this last two trips.  I am not greatly worried about either 8 or 10 MPG, since I was really only counting on+/- 8 anyway.  If I get over 8 MPG I guess that's just a bonus while towing.  I just did not want something to be wrong with the coach or the toad set up.   

Being new to the RV Forum  I do appreciate the information.

Thanks again,

Bob
 

Gary RV_Wizard

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In flat country I'd agree with you, Gary. But in the western mountain regions, you get lots more penalty for going up the hills with the extra weight but don't gain a corresponding amount on the downhill swing.

Isn't that what I said?

Repeating:
Weight is not much of a factor on level roads - just a small increase in the rolling resistance from 4 additional tires on the road. Climbing grades, however, means every pound is extra load to drag to the top of the hill (and to brake on the way gown, too). You might see a substantial hit in hilly terrain.
 

DIY-Guy

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With our 2009 Winnebago Aspect 28B, Ford 6.8L V10 Gas, we have averaged 7.84 mpg over 13,200 miles pulling a Nissan X-terra flat.  We almost always pull the toad, but have about 1,300 miles on the Aspect without it, averaging 8.90 mpg.  Both totals are a fair mix of flat and mountainous terrain, secondary roads and interstates.
 

blw2

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Gary touched on it when he mentioned something about bio diesel blends, but something I think that is often missed is gasoline blends.  (I don't know about diesel)
with gas
there are seasonal blends
and regional blends
& i can only assume variations in ethanol content
all of which will affect the numbers to some degree.
 

Lou Schneider

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Right.  On several different vehicles, my gas mileage has gone up by 10-15% as soon as I burn my first tank of non-California gas.

Works the other way when I re-enter CA also.
 

Arch Hoagland

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Lou Schneider said:
Right.  On several different vehicles, my gas mileage has gone up by 10-15% as soon as I burn my first tank of non-California gas.

Works the other way when I re-enter CA also.


Hmm..I don't see that when I'm out of the state, wish I did.

I do notice lower prices on gas and less traffic though.
 
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