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Old 01-06-2016, 09:04 PM   #1
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Horsepower vs mileage

We are newbies to the forum and look forward to hearing your opinions. We owned a 2002 Monaco Diplomat 40PDQ with a 330 hp Cummins. We pulled a Jeep Liberty as our toad. Our only issue wasn't so much the fuel mileage but the lack of power pulling in the mountains. We sold the coach several years ago because we didn't have the time to really enjoy all the things the rv lifestyle has to offer. We have since retired and want to buy another coach. The question is we are looking at several 40 ft coaches that have over 500 hp engines. We love the idea of the extra hp and torque but how much will our fuel mileage suffer ? Any thoughts on the pros and cons would be appreciated.
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Old 01-06-2016, 09:26 PM   #2
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My 300 HP Cummins pulled my Excursion and Nissan Murano thru the Tennessee mountains fairly well last year. Our new coach has a 380 HP Cummins. Haven't towed with it yet, but I'm pretty confident it's going to do just fine with our 40' Discovery. Unless you're sure you'll be pulling heavy loads through the mountains all the time, I'm not sure you need a 500 HP. You're certainly going to pay extra for it.

As far as mileage goes, does it really make a difference if you get 7 MPG or 10? Seems to me even when diesel goes back up (and count on that happening) a 30% hit in mileage would be the least of my concerns.

Good luck in your search
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Old 01-06-2016, 09:42 PM   #3
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Quote:
Originally Posted by Bobbyt View Post
We are newbies to the forum and look forward to hearing your opinions. We owned a 2002 Monaco Diplomat 40PDQ with a 330 hp Cummins. We pulled a Jeep Liberty as our toad. Our only issue wasn't so much the fuel mileage but the lack of power pulling in the mountains. We sold the coach several years ago because we didn't have the time to really enjoy all the things the rv lifestyle has to offer. We have since retired and want to buy another coach. The question is we are looking at several 40 ft coaches that have over 500 hp engines. We love the idea of the extra hp and torque but how much will our fuel mileage suffer ? Any thoughts on the pros and cons would be appreciated.
Well,
The first thing you need to do is, STOP worrying about fuel mileage. As you already know, you're going to be driving a KLEENEX box. There's no aerodynamics in a rolling gymnasium. And, while having a larger, 500HP engine is great, the additional weight of a larger coach, that comes with that 500HP power plant consumes much of that additional HP.

Yes, you'll notice the difference from your older coach, no doubt about that. But, there are no rocket ship motor homes out there. Some are better than others. But face the fact that, even the largest engine ones slow some on hills and grades. Oh, they might make it up the hill faster than you're used to but, you'll still see some slowing down.

Our coach, an '04 Itasca Horizon 36GD with the C-7 330HP CAT, runs down the road nicely even with 6700 lbs. worth of toad and motorcycle attached. It does slow down on quite a bit on some of the steeper grades. It is what it is. I ALWAYS get to the top.

We hover between 6.5 mpg and 8. It's ultra rare for us to get into the 8s but, it does happen every now and then. Lousy fuel mileage is part of RVing. You don't buy one to get good mileage. Ain't happening. Oh, you'll read claims of upwards of 10 by some on here with large Diesel rigs but, I'm kind of a realist. When your pushing that kind weight, and up some of Americas super grades, mileage is non-existent.

The point is, you've lived long enough to get to retirement. You want to enjoy what America has to offer in terms of places to go and see, people to meet, fun things to do, and more, then write off the mileage.
Scott
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Old 01-06-2016, 09:51 PM   #4
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I use 7.5 for figuring. Our DSDP with 350 ISC (then added a Banks for 435/1200) would do between 7.5 and 8 overall over 48,000 miles.
With the present rig the VMS shows an overall of 7.6 for 45,000 miles. As to slowing down on the hills, I haven't noticed it at all. Go up the Grapevine on cruise control at 55 with no drop in speed and I can easily recover if I get slowed down by traffic. However, there aren't many 650 hp rigs out there either. Our empty weight is 46,000#'s so I figure 7.6 is good enough, especially since I still get that mileage loaded and towing a Honda Odyssey.
At 60 mph I'm showing 1350 on the VMS and tach. Rear gearing is 4.3 with the 315/80 drive tires. The calculated "sweet spot" for mileage is 1375 according to Cummins.
I wasn't worried about the fuel mileage, if I was I'd be driving a Prius and staying in motels.
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Old 01-06-2016, 09:55 PM   #5
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Sounds like you're looking at a bit higher up the food chain coaches this time around, as usually 500+ HP coaches are in the upper side. As mentioned, these usually are a bit heavier too, based upon content, possibly tag, beefier suspensions, if all electric they can have more batteries, etc.

That being said, quite often coaches with the larger block engines, more HP and more torque - do not work as hard moving down the road, or up the hill. They can yield the same, and sometimes better MPG then a small or midsize block, that could be working too hard to move the load of a coach thru the woods.

Gearing can also be different in the rigs with bigger engines, and that has an impact on MPG too.

Their are a few engines to avoid, so I recommend when you are looking for a coach, find out the specific engine that is producing that HP, and check up on that specific engine.

And you probably know the strong recommendation that is repeated quite often. Choose the coach that you like as far as interior design and livability - as that usually trumps everything else!

Best of luck on your search, happy hunting,
Smitty
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Old 01-06-2016, 10:14 PM   #6
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Scott hit a home run again.
We have a 400 Cat and get 6.7 to 8.4 pulling a Honda Accord but we just got a Ford Edge 1500lbs more but I'm going to spend it before the kids get it, so if I get 6.2 great.
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Old 01-07-2016, 07:11 AM   #7
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If you buy a Motorhome, Gas or Diesel, and worry about the fuel mileage then you probably should not buy a Motorhome...Just my opinion.....

I use a Pilot/Flying J card because of the .06 per gal. discount and every time I pull in to the pump I keep the receipt and when you look at the savings I have saved 1 to 2 bucks on a fill-up..........It is what it is and I just fire up that bad boy and tell my boys they need to make their money for retirement cause Mom & I are spending their inheritance......

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Old 01-07-2016, 07:54 AM   #8
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I don't think it matters much whether you have 300 HP or 600 HP. Depending on driving conditions, the speed driven, and the total weight being moved, your mileage is going to land somewhere between 6.5 and 8 mpg. Anything consistently lower or higher is uniquely exceptional in my opinion.

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Old 01-07-2016, 09:58 AM   #9
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Scott hit a home run again.
We have a 400 Cat and get 6.7 to 8.4 pulling a Honda Accord but we just got a Ford Edge 1500lbs more but I'm going to spend it before the kids get it, so if I get 6.2 great.
2 stroker

Hi Stroker. Can you tow the Edge 4 down? Do you have to do anything special to the Edge? How do you like it

Hurk
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Old 01-07-2016, 10:13 AM   #10
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Let's see. 8MPG and boondock for the night........OR
drive a car ....30MPG and $150/night for food and motel.

Guess my MPG just went sky high.

Relax, and enjoy.
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Old 01-07-2016, 11:14 AM   #11
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MPG

Your MPG will be governed by you right foot.
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Old 01-07-2016, 11:20 AM   #12
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Your MPG will be governed by you right foot.
Yup. It take so much HP to move a particular MH at a set speed.

Whether you have 100 or 500 HP, if it takes 90 HP, you will burn enough fuel for 90 HP.

If you need fast acceleration or more hill climbing power, down goes the mileage.
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Old 01-07-2016, 11:29 AM   #13
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horsepower

Quote:
Originally Posted by Bobbyt View Post
We are newbies to the forum and look forward to hearing your opinions. We owned a 2002 Monaco Diplomat 40PDQ with a 330 hp Cummins. We pulled a Jeep Liberty as our toad. Our only issue wasn't so much the fuel mileage but the lack of power pulling in the mountains. We sold the coach several years ago because we didn't have the time to really enjoy all the things the rv lifestyle has to offer. We have since retired and want to buy another coach. The question is we are looking at several 40 ft coaches that have over 500 hp engines. We love the idea of the extra hp and torque but how much will our fuel mileage suffer ? Any thoughts on the pros and cons would be appreciated.
the bigger engines avg about 7.5 mpg , some less , and the 330 avg about 10 mpg
so consider about 1/3 more fuel
if you are planning lots of miles your wallet will hurt
but , you will get up the hills faster


Bev and Allen
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Old 01-07-2016, 12:07 PM   #14
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Your MPG will be governed by you right foot.
I notice a big difference between 65 MPH and 70Mph
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