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Motorhome Tag Axles, Length and Fuel Mileage

40 foot motorhomes miles per gallon

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#1 ultraglide


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Posted 16 February 2014 - 08:17 PM

My wife and I are looking to purchase a new motorhome.


We were thinking of getting one that is 42-foot or larger. We have been told that our fuel mileage will be worse and we should stay with a 40-footer.


On our coach now we get about 7 to 8 miles per gallon depending what direction we're going.


Anyone have any ideas or comments?

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Posted 16 February 2014 - 08:26 PM

The bigger the coach, the heavier the coach the worse the mileage is going to be.  At  42' or longer, you'll have to get a tag axle coach...more storage capacity, more weight.  My coach is a model 40X which is actually 1/2" shy of 41'...it's as big as I can get without a tag.  If you need or want lots of space, you'll need the bigger coach and the tag.  If you don't need the storage or space, get a coach that is less than 42' and a single axle.  We opted for the single axle...and have more space than we can fill.

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#3 wolfe10


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Posted 16 February 2014 - 08:27 PM



Welcome to the FMCA Forum.


MPG is a reasonably complex issue.


On flat ground, added weight is far less important than on any upgrades.


On the flats, aerodynamics is the main issue. 


But (and that is  BIG but), fuel is not the largest expense unless you drive a lot of miles.  Depreciation far overshadows fuel expenses for most RV'ers.

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#4 BillAdams


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Posted 16 February 2014 - 09:10 PM

As Brett mentions, fuel is going to be one of your lesser expenses compared to everything else.  I should say the "difference" in fuel mileage.  If your current coach get 7-8 and the new one gets 6-7 (unlikely anything would get less) then you are only worrying about 1-2 MPG.  In other words, over the course of 10,00 miles that would be less than 200 gallons per year or less than $1000.

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#5 kaypsmith


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Posted 16 February 2014 - 10:00 PM

I personally like the drive and ride comfort of a coach with "Tag Axle". I average 8 plus with my MCI, which is called 40 ft, but a tape pulled stem to stern shows 41.5.

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#6 bobbyks


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Posted 17 February 2014 - 09:44 AM

I have a 45 ' Mandalay, 425 Cummins with tag, getting same mileage as previous 40 Damon 325 Cat, 6-7 mpg.


The ride is greatly improved with tag. Towing Jeep Wrangler on both coaches.


I also have better steering ability, can get in and out of places I could not with the Damon.

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#7 Medico


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Posted 18 February 2014 - 08:36 AM

I am also getting 6.3 mpg overall with my 45 foot tag axle with a 525 HP Cat C13 engine, and this is over both hills, mountains and plains. It's more important to watch the speed rather than the tag for mileage. For example I generally set my cruise at 62 mph or so. If I bump that up to 70 my mileage drops to 5 to 6 mpg and so forth. My mileage does not change much whether I'm towing my toad or not. Aerodynamics and speed are much more important.


As already stated, the ride with a tag will be far superior.


My sister-in-law with a 23 foot Class C only gets about 7 to 8 MPG.

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FMCA #F431170, GS #822128658, Escapees SKP #112655


2006 Country Coach Magna (525 HP Cat C13 1650 torque, Alison 4000 6 speed tranny), 2012 Jeep Liberty




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