Review on the new 7.3 Ford V*

Gjac wrote:
How much difference in mpgs or handling between a B+ aero front end and a C with the overhead bed? Does anyone have any data on this? I think it is logical to believe a B+ is better but how much better. The trade off is more room vs better mpg. If only 1 mpg I would choose more space. If the difference was 4mpgs 10 vs 14 mpg I might choose the B+.

That is a very good question. I have no supporting data, only my gut feeling based on reading years of comments from other people regarding their own fuel economy. Comparing our aerodynamic rig to a typical class C of the same length with bad aerodynamics, the difference is not more than 20%. But there are just too many factors to state a reliable figure. Like others mentioned, aerodynamics are more critical if you cruise at 70 mph versus 60 mph. Some people live close to terrain. We drive across the Great plains under better mpg conditions, factors like that.

There are unrelated benefits to having a seamless B+ cap, primarily avoiding the resonation of the over-hang which encourages seams to leak on a class-C as it ages.

I think you’ll find the issue of fuel mileage is tied far more to the drivers right foot than it is the aerodynamics.

The ‘sweet spot’ of the drivetrain is also important. For a few years my father & I both had exactly the same make / model / drivetrain Class A’s. He swore up & down that driving slower, 60 mph gave him the best mileage. I disagreed. Then we went to the same place at the same time. He held 60, I drove 65 - 70. Low & behold my rig used less gas to do the trip.

Regarding the mileage difference between a C and a B+, I can only offer anecdotal evidence. Our Sunseeker gets 9 1/2 to 10, where my nephews Chevy pickup with the same engine, a 6.0L, always got 12. And that's just a pickup.
As far as the Ford engines, it's probably a lot of the same story. The V10 is a gas guzzler, no matter what, and I wouldn't expect much different out of the new Ford V-8.
But oh the power difference…

ron.dittmer wrote:

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Some motor homes are flat-faced compared to others built on the same chassis. Then there is the size of the face. Some rigs are taller and wider than others. Given equal weight and identical chassis, a worse-case versus best-case scenario, you would see a change in fuel economy. How much? Who knows. But based on numbers shared over the years, I estimate a 10% difference.

A class C (B+) a best case scenario with aerodynamic cap, angled transition walls, narrow body, and lower roof.


I wish I could find a better worst case scenario, but here is something.

How much difference in mpgs or handling between a B+ aero front end and a C with the overhead bed? Does anyone have any data on this? I think it is logical to believe a B+ is better but how much better. The trade off is more room vs better mpg. If only 1 mpg I would choose more space. If the difference was 4mpgs 10 vs 14 mpg I might choose the B+.

ron.dittmer wrote:

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Aerodynamics have a much greater effect on fuel mileage than weight for highway driving. On level ground and at a steady speed, the only effect weight has is to (slightly) increase the rolling resistance of the tires. Air resistance, on the other hand, make up the greatest part of the friction that must be overcome, and further it goes up tremendously with speed increases--it's proportional to somewhere around the cube of the vehicle speed, if memory serves.

For climbing hills, and for stop and go driving, the weight is relatively more of a factor than for highway cruising.

The aerodynamics of the rear of the vehicle are at least as important as those of the front. RVs generally are pretty terrible at both ends; a squared off back generates lots of turbulence and drag, which is why airplanes and Priuses tend to have pretty pointy backs.

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Some motor homes are flat-faced compared to others built on the same chassis. Then there is the size of the face. Some rigs are taller and wider than others. Given equal weight and identical chassis, a worse-case versus best-case scenario, you would see a change in fuel economy. How much? Who knows. But based on numbers shared over the years, I estimate a 10% difference.

A class C (B+) a best case scenario with aerodynamic cap, angled transition walls, narrow body, and lower roof.


I wish I could find a better worst case scenario, but here is something.

alvinator wrote:
CaptJD wrote: Well, last Wednesday I've purchased a Thor Coleman 19CM and it came with that 7.3 engine.

The smallest Coleman Class C motorhome on their website is a 22CM. Where were you able to find a 19CM?

That model and size sounds like a rental unit that Thor makes.

CaptJD wrote: Well, last Wednesday I've purchased a Thor Coleman 19CM and it came with that 7.3 engine.

The smallest Coleman Class C motorhome on their website is a 22CM. Where were you able to find a 19CM?

btim wrote:

My E-450 I has the 4:10 rear end and 6 speed trans. At 65mph the engine is turning about 2300 rpm. The engine stays in the powerband in 6th gear at highway speeds so there is no downshifting for overpasses and bridges unless they have very steep inclines.

I forgot the de-tuned 7.3s still get the old 6 speed trans (5th and 6th basically like 8th and 9th in the 10 speed).

It's a decent pairing since the 7.3 has power for days.

If the OP's little van has 4.10s as well, I can see how he thinks it's getting high rpms at highway speeds though. But it should pull like a train!

What rpms in 10th gear at 70-80-90mph?

My E-450 I has the 4:10 rear end and 6 speed trans. At 65mph the engine is turning about 2300 rpm. The engine stays in the powerband in 6th gear at highway speeds so there is no downshifting for overpasses and bridges unless they have very steep inclines.