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Discussion Starter #1
The latest MotorHome issue that just came out reviewed the ProMaster-based Winnebago Trend 23L model and gave it a fairly good review.

It's a Class C (based on "cutaway" chassis) that is 24 feet long, and 90.5 inches wide. Height is 10ft-4in. Total unit weight as tested was 8,180 pounds (empty). Occupant and cargo carrying capacity was 1,170 pounds.

What impressed me most was the 15.65 MPG they got. It didn't really say under what driving conditions, but that's not bad for such a large box on wheels. A standard van driven conservatively should do better.

Also of interest was the power. Zero to 60 MPH only took 15.4 seconds. That's excellent for an RV.

Out of curiosity I looked at previous tests of similar units and found the 2009 Itasca (also Winnebago) Navion IQ 24DL. The profile is almost identical but is about a foot longer and has a rear outback-style slide.

Again they didn't cover what type of driving, but the Sprinter-based Navion got 17.7 MPG. Power out of the 154-hp diesel was much less though. At 2500 RPM it ran between 65 and 70 MPH on flat ground. For the uphill test they climbed Gaviota Pass with a 6 percent grade, and the Sprinter went up in 4th gear at 58 MPH at 3650 RPM.

I found this hill-climb data interesting because it shows that even diesels need RPMs to climb at a faster speed. That's how they get power too. And 3650 RPM for a diesel isn't the same as if it were a gasoline engine. That's getting up there.

I looked at a couple of other recent Sprinter class C reviews and the mileage was generally lower -- in the 15+ range -- but the units were not only a little heavier but also slightly wider and taller (making them less aerodynamic). If a find a better comparison that is more recent I'll post it later.

If interested in small Class Cs the MotorHome review is well worth reading.
 

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We owned a 2009 Itasca Navion IQ DL Sprinter class C. Whoever took that motorhome up that mountain at 3600+ rpm is an ignorant diesel driver.
The Sprinter V6 will do 48 to 50 mph at 2800 rpm in 3rd gear all while getting 14+ mpg with a LOD of less than 65%.

You don't run a diesel at high rpm to get your power and mileage.....
 

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The Trend is one of a few motorhomes I'm looking at, with the Travato, and a Sportsmobile upfit being the main candidates.

There are a few unique features which make the Trend particularly enticing:

1: The 23L is the floorplan that has a corner queen, and a drop-down bed. In theory, it can sleep six. For such a small vehicle, that is pretty cool. The other floorplan, the 23B has a bigger kitchen and bathroom, but you are forced to use the drop-down bed (which may be a lousy thing when you just want to park, walk to the back and lie down.)

2: It has on-demand hot water. On full hookups, this means as long a hot shower as you desire. Not many rigs except the higher end diesel pushers offer this standard.

3: It looks modern. In Europe, it would look commonplace, but those type of rigs here stand out.

Of course, no slide-out can be a downside to some, but motorhome choices are always subjective. It also is a gasser, so don't expect the diesel oomph (especially with a conventional automatic transmission as opposed to the upcoming AMT), but it is a nice motorhome for people who don't have much space to store one... and might be able to be used as a secondary driver in a pinch.
 

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Discussion Starter #4
We owned a 2009 Itasca Navion IQ DL Sprinter class C. Whoever took that motorhome up that mountain at 3600+ rpm is an ignorant diesel driver.
The Sprinter V6 will do 48 to 50 mph at 2800 rpm in 3rd gear all while getting 14+ mpg with a LOD of less than 65%.

You don't run a diesel at high rpm to get your power and mileage.....
I'm certain that fuel economy is not the primary objective of the hill-climb test. They determine how fast any RV they test can climb a given grade. From previous reports I've read they often use long grades of 6 percent or so.

If fuel economy was the goal, I'm sure they would climb slower at lower RPMs where the engine is more efficient. But this test is to tell whether an RV can go up at 58 MPH, or 42 MPH, or 70 MPH.
 

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Ok I see what they were getting at. I can tell you one thing, both of our Sprinter V6's leave any gasser RV's we've been around or in, in the dust going up a mountain. Namely the Ford class C's. Here they are going along at 40 to 45 mph up the hill just literally SCREAMING with rpm. We are able to pass them at will, no issues.
That's one good thing about the Sprinter I like.
Now when the Transit EcoBoost comes around, I expect it to drive and climb like the Sprinter diesel
 

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Discussion Starter #7
Ok I see what they were getting at. I can tell you one thing, both of our Sprinter V6's leave any gasser RV's we've been around or in, in the dust going up a mountain. Namely the Ford class C's. Here they are going along at 40 to 45 mph up the hill just literally SCREAMING with rpm. We are able to pass them at will, no issues.
That's one good thing about the Sprinter I like.
Now when the Transit EcoBoost comes around, I expect it to drive and climb like the Sprinter diesel
I think it depends greatly (or mostly) on power-to-weight ratio of the loaded vehicle. And available power depends on elevation more so for naturally aspirated (i.e. - non-turbo) gasoline engines.

Many large Class Cs on Ford E-450 chassis are hauling around much more than Sprinters can. Most Sprinter Class Cs are around 24 to 25 ft long while large Fords can easily exceed 30 feet. Even so, assuming owners don't overload either unit, the Ford should have a slight power-to-weight advantage over a loaded Sprinter.

At higher elevations the Ford Class C, which typically have 305 HP, will lose up to 40 percent or more of its power on high-elevation mountain passes. At those elevations the turbo in the Sprinter will avoid as much engine power derating, which likely makes your Sprinter climb faster.

Compared to smaller Fords climbing steep grades near sea level I'd expect a different outcome. At least that was my experience with a small V10 Ford Class-C I owned. It didn't climb as fast at 10000 to 12000 ft crossing Colorado, but at lower elevations it seem to leave all diesels behind.
 

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Discussion Starter #9
If we looked at BSFC (brake specific fuel consumption) maps of various engines, we'd find that diesel and gasoline engines follow similar trends. The overall shape of the maps would appear very similar, even though the specific numbers would be different.

Both diesel and gasoline engines tend to be most fuel efficient at lower RPMs, and both produce most power at higher RPMs relative to their speed range. So given same driver goals the same should apply to both. The same high versus low RPM argument would apply to both.

If a driver wants to save fuel, it's best to use RPMs somewhat below the engines' maximum torque rating. For a Sprinter V6 that's in the range of 2400 RPMs or lower. For a PM V6 that's well below 4000 RPM.

On the other hand if a driver wants to pass, climb, or drive into a head wind as fast as the vehicle was designed to go (ignoring fuel consumption entirely), then both diesel and gasoline engines must be operated at full throttle near their respective maximum-horsepower RPMs. For the Sprinter V6 that's 3800 RPMs and for the PM V6 it's 6400 RPMs.

The biggest difference is that gasoline engines can spin faster than diesels. And if diesels could spin faster they would. Over the years engineers have worked very hard to design diesels that can now run at or above 4000 RPMs.

In my opinion "high" versus "low" RPMs is relative. When placed in relative context to engines' speed range there isn't that much difference.
 
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