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Old 03-31-2016, 10:44 PM   #1
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Question RPM question

I just bought a 2012 Thor Hurricane 30Q. So far, we love it. We are doing our first trip this weekend.

I had a quick question. What RPM's are you guys running on a fairly flat terrain and running 60-65 mph?

I am running about 1800RPM at 60mph and 2000RPM at 65mph. I just filled up my tank and it says "551 miles to empty", that would mean the coach has been getting about 6.8 mpg on average (80 gallon tank). That sure seems low being that it is running at such low RPMs on the highway.

Thoughts?
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Old 03-31-2016, 10:54 PM   #2
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Well to me that all sounds about right but would think you might do just a little bit better. Check air in tires and engine air filter... You really need to go thru about a hole tank of fuel to really tell.
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Old 04-01-2016, 01:05 AM   #3
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The 'miles to empty' is a gauge on when you need to refuel - but not completely accurate to calculate actual mileage... it adjusts assuming your current driving conditions continue till end of tank...
In my car I can start a trip with 60 miles to go - get on the highway for 30 miles and still have 45 miles to go...
I'd suggest filling tank and recording odometer - then compare at next fillup and calculate actual mileage.

Your RPMs sound about right... I'd expect slightly better mileage if not towing.

2014 Hurricane - I've gotten about 8mpg not towing and in the 6-7 range when fully loaded (close to max weight) and towing approx 4000 lbs (and not all flat...) Haven't calculated this last long trip yet. (I also don't typically stay at 60-65 unless weather/road conditions are bad... I know I pay a price for that too.)
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Old 04-01-2016, 03:41 AM   #4
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Quote:
Originally Posted by ghoticov View Post
....cut....

I am running about 1800RPM at 60mph and 2000RPM at 65mph. I just filled up my tank and it says "551 miles to empty", that would mean the coach has been getting about 6.8 mpg on average (80 gallon tank). That sure seems low being that it is running at such low RPMs on the highway.

Thoughts?
Your observed RPMs are not consistent with 2011 or 2012 Ford specifications for the chassis Thor used on the 2012 Hurricane 30Q. The Thor Hurricane Catalog shows the 30Q being built on 16,000-pound F-53 chassis with 190-inch wheelbase. And according to Ford specs you should be running higher RPMs at 60 or 65 MPH. It's possible you could have taller final gearing than what is standard, but that's not very likely.

Regardless, engine RPMs is a poor way to estimate fuel economy because it doesn't reflect how hard the engine is working (there isn't a direct correlation). Your V10 may get 8 MPG at 2,000 RPMs, but in my van would likely get around 16 MPG at same 2,000 RPM. Engine RPM makes some difference, but what's more important is how hard the engine is working.

By the way, I also like the 30Q because it's one of the last Class A motorhomes made without a slide, so I've done quite a bit of research on it. I expect you should get at least 8 MPG at steady 60~65 MPH on Interstate if not running generator. If you get much less than 8 MPG, I would certainly appreciate you reporting your actual MPG.
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Old 04-01-2016, 04:02 PM   #5
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We had Ford V10 F350 4x4 pickups at work with just toolboxes with tools & they got 8 mpg regardless until you hooked a trailer to them & then it dropped to 6 mpg & in Fords wisdom they put 25 gallon gas tanks on them.
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Old 04-01-2016, 04:22 PM   #6
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2014 Thor Class-C
24' on a E350 chassis
4.10 axle
Motorhome = 11k lbs
Trailer & toy = 3k lbs
60mph @ 2100rpm = 10mpg
65mph @ 2400rpm = 9-9.5mpg
Hand calculated at pump
(gals filled miles driven)

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Old 04-01-2016, 06:22 PM   #7
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Quote:
Originally Posted by BCRacing24 View Post
2014 Thor Class-C
24' on a E350 chassis
4.10 axle
Motorhome = 11k lbs
Trailer & toy = 3k lbs
60mph @ 2100rpm = 10mpg
65mph @ 2400rpm = 9-9.5mpg
Hand calculated at pump
(gals filled miles driven)
That's more like what I would expect. I got around 8.7 MPG (from memory) on a 5,000-mile trip on a 31-foot Class C built on E-450. And it was loaded down. Generator use was minimal.

The Hurricane may be slightly heavier (depending on how it's loaded), but I also expect the Aerodynamics of Class As to be better than that of conventional Class Cs (B+ should be a little better).

I'm not looking at motorhomes based solely on fuel economy because total cost of ownership goes well beyond cost of gasoline, but having said that, would personally budget 8 MPG for a Hurricane 30Q versus 10 MPG for newest Axis/Vegas.

A compact Class A would have to get 12 MPG at 60~65 MPH before it would make a big enough difference to sway my next purchase.
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Old 04-01-2016, 09:46 PM   #8
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So much for our first trip this weekend, the whole family is sick.

Thanks for the info guys, I will be sure to report back in a few weeks once we actually take our trip... I should have a better idea on what my mpg is.
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Old 04-03-2016, 11:08 PM   #9
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G,
Here's what I have after several tanks fills. This is the average based on my fuel log for gallons used and miles covered. It's not broken down to with toed or without, going over mountains or flat terrain. We average about 7.2 MPG. Some tanks we got a lot better than others, because wind affects the mileage more than I originally thought it would.
Also driver habits will help or really hammer gas mileage.
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Old 04-04-2016, 04:09 PM   #10
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Engine isn't the main problem

The Ford V10 is a fairly efficient engine, and can deliver decent MPGs as long as power requirements aren't too high.

I just drove from south Florida to Texas in an E-350 van with the V10, typically around 75 MPH. It took three tanks of gasoline, with the last one going 415 miles on 27.456 gallons, for an average of 15.1 MPG.

Obviously my van is much smaller and lighter than Class A motorhomes, but it shows that the V10 is not inherently a gas guzzler like many report.

The biggest problem is in how much power the V10 is asked to make, not on RPMs or poor engine efficiency.

Roughly for comparison:

Large Class A = 100 HP at 60 MPH

BSFC = .41 pounds/HP-hr

Fuel rate = 41 pounds/hr = 6.8 gallons/hr

MPG = (60 miles/hour) / (6.8 gallons/hour) = 8.8 miles/gallon


Smaller E-350 Van = 50 HP at 70 MPH

BSFC = .55 pounds/HP-hr

Fuel rate = 27.5 pounds/hr = 4.6 gallons/hr

MPG = (70 miles/hour) / (4.6 gallons/hour) = 15 miles/gallon


Notice that in reality a V10 is too large to operate as efficiently in a small and light-weight van yet it gets almost twice the MPGs. If my engine wasn't so large that it operated inefficiently (estimated .55 vs .41 pounds/HP-hr), and was downsized in proportion to required power (roughly half the engine size -- like in newer Ford Transit vans), I would get just over 20 MPG at 70 MPH.

There isn't that much wrong with V10 other than it may be too large to be as efficient in smaller motorhomes like Axis and Vegas. And if motorhomes are made slightly smaller and lighter (like Winnebago Reyo in size), then they will need smaller engines for maximum efficiency. Maybe that's why Ford will soon offer the 6.2-liter V8 in E-series.
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