Same exact Class C / Different engine miles per gallon

[VocalVirgo]

Originally Posted by AJMike

This always puzzles me. Someone asks a perfectly reasonable question about relative fuel economy numbers and responders post telling him or her that if they are concerned about this they should not buy an RV. Yet when someone posts about the fuel reimbursement program they always get responsive replies. Both questions are about saving money on fuel but the first is ridiculed and the second is respected. As I said, it always puzzles me.

Do I think about how much fuel is going to cost me? Sure. Do I take it into account when looking at new RVs? Sure. My wife and I have been RVing for perhaps 20 years now and I always think about fuel costs. Does it mean we should not have been RVing for the past 20 years? I don't think so.

It seems perfectly reasonable to me to be thinking about fuel costs when you plan to buy an RV. It is probably the largest monthly budget item for your RV so unless you don't care about your money you have every reason to think about it and plan accordingly.

Thank you for this. Very well said.
And on top of that I was actually asking for an apples to apples comparison. Same exact coach, different cutaway/engine.
From what I’ve gathered so far, the Chevy 6.0 probably gets 10% or more better fuel economy. Obviously it has less power. Let’s see if I can even find one on the chassis once they start building again and shipping. We will see.

[sibe]

vocal....

do not count out the new ford 7.3 the jury is still out...

the GM 6.0 is a worker motor and the gm chassis in good just not as popular..

I have a GM 6.0 in my shop.. has some miles on it, pulled a fifth wheel etc.. just did exhaust manifolds and new brake lines as they rusted away.. I normally do collosion repair but my one worker likes this stuff, i filp him a bone..

Owner said he gets 10-12 mpg since new, 3500HD, 4 dr, 4x4.. same base motor as the RV.. towing hard, 8-9 with his 34 foot 5th..

just throwing verified info..

I just rack my brain when apples to apples come up.. there are different apples so.....
like i have stated in past.. like many of you all.. I go to events that have 80-200 rvs on weekends.. all flavors.. A,B,C TT..etc..
We always compare notes.. many notes are in braille or taken with a grain of salt IMO
I have had a 86 460 small class c, a 94 e350 shuttle conversion 460.. current 96 minnie e350 460..
I was able to tweek the 86 with a carb to get 10-12mpg all day, never towed.. headers, edelbroc tuned carb, msd ign,, rv cam.. worked heads from early 429 t bird.. need good prem fuel.. and another gear..

the 94 and 96, are the same beast IMO.. I have tuned, played and optimised.. towing 6.5-7.5.. by themself I have seen 9 mpg with a good fuel and no head wind LOL

Traveling buds.. 460 powered.. shorter 24ish would see the 8-9 alot, 28-31 ..saw 7-7.5 in real talk, not that one off trip

V10 can vary as there are a couple versions .. A guy I traveted with , maine to fla.. had a 2010 winnie 31 foot, small trailer .. 5.5-6.5 was his gig, no trailer he would add 1.. I would at times take my 302 hitop ford custom van, and trailer to ease my wallet.. it would do 8.5-9 best.. people would tell me their 302 would to 14-18... maybe a gutted open van..

My points are mpg can vary .. some tuner v10 I do not doubt bursh that 9-10 mark alot..

I would really like to see a Super C based on the F series nose with a new diesel, tuned proper,, I think 14+ is very very real..
Ford C class e450 eng compartment is not made well for a diesl IMO..

[Bobby F]

Originally Posted by TXiceman

You don't buy an RV to get good gas mileage.

At the same time, you don't ignore the subject if there are true differences.

And, if we make certain choices this November, I'd not want to bet my budget on $2 gas. Maybe $5.

[VocalVirgo]

I’m in California. I have seen gas and diesel above $5.00/gallon many times.

I had 2 vans before... just sold the second one. Nothing is going to get that mileage, but the difference between 10 and 7 is a huge deal. I’m planning on the smallest model (24’), and I think the Chevy 6.0’s (that are still unbuilt) are going to give better MPG on flat ground. I dunno. We’ll see. H*ll, maybe I’ll end up in another van...

[AJMike]

Originally Posted by VocalVirgo

Thank you for this. Very well said.

No problem.

I have considered gas (and diesel) economy with all 5 RVs that I have owned over the last many years, and I suspect that is true for most people who buy Bs and Cs. Perhaps not so much the large diesel pusher As, but probably also for the smaller As. It may only be one factor in many, but it is something I have always thought about.

The idea that this means I should not be buying an RV just seems very odd to me.

Originally Posted by VocalVirgo

From what I’ve gathered so far, the Chevy 6.0 probably gets 10% or more better fuel economy. Obviously it has less power. Let’s see if I can even find one on the chassis once they start building again and shipping. We will see.

While I have no plans to buy another RV anytime soon I would be interested in seeing what you find out about the relative merits of the different gassers. My present RV is a diesel, and I was happy to trade the initial higher cost in exchange for lower monthly fuel bills (we get about 18 mpg on average) but that might change in the future.

Please keep us posted.

[Unclepaul]

No matter what posters say, most everybody considers fuel costs in their RV buying decisions. That is how guys are wired.

Ford and Chevy V-8's are of similar design, with the Ford 7.3 being larger and newer production.

Ford marketing people claim they have tuned it to produce more torque, lower in the range. Calculated stoimetric efficiency where the motor will be spending most of it's time cruising. They claim this will also result in a quieter motor, with less annoying downshifting.

Results from Pickup owners with these engined do not claim much increase in fuel economy, but love the sound and pulling power down low. Chevy is a smaller displacement and probably will need to pull at higher revs to maintain the same speeds up hills.

Imagine that fuel economy will be similiar, with a slight edge going to the newer Ford Godzilla.

Do not know of anybody that has one of each of these with exactly the same RV to give OP a precise answer.

Do now that most all RV manufacturers of budget priced rigs are going to either the Ford 7.3 or the smaller displacement Transit Turbo V-6. Imagine the smaller rigs with the V6 will get much better economy and snappy performance, but suffer from lack of towing and carrying capacity.

[Ron Dittmer]

Hi VocalVirgo,

You sure got some interesting feedback, and here is mine.

Our class B+ motorhome PICTURES HERE is 23'-8" long with an aerodynamic configuration. It is built on a 2007 E350 with V10 and the previous generation Torqshift transmission with one less gear than the current-day E350/E450. It does have the typical E350 rear axle ratio of the time that was more fuel efficient than the axle ratio of the E450.

Our fuel economy (4000-6000 mile trip averaging) is fairly consistent.
10.5mpg not towing another vehicle (max speed limited to 60mph)
9.25 when towing our Jeep Liberty (max speed limited to 70mph)
I would have thought going faster with the Liberty in-tow would be worse yet, but I attribute that to the aerodynamics of our motor home.

I heard rumor that the new 2021 E350/E450 with the 7.3L-V8 engine will have improved fuel economy over the 6.8L V10 of 2019 that it replaces. How much is not known.

In the case with a conventional class C that is not aerodynamic, your fuel economy will be greatly influenced by your cruising speed. The trouble with the 6.8L-V10 and with the 7.3L-V8 engine, is that the power from the engine gives the driver the confidence to drive faster. Limiting your cruising speed between 60mph and 65mph might increase your fuel economy as much as 20%.

I don't think you can go wrong with the 7.3L-V8 engine & transmission combination, especially with a 2022 model year to avoid some of the little quirks of first-year production.

So comparing the new Ford chassis with the current Chevy chassis, I think they will be exceptionally comparable with regards to fuel economy, but the new Ford engine will have more power to spare which if not respected, will lower your fuel economy.

[AJMike]

Originally Posted by Ron Dittmer

10.5mpg not towing another vehicle (max speed limited to 60mph)
9.25 when towing our Jeep Liberty (max speed limited to 70mph)

I just have to ask - why is your limiting speed when not towing lower than when you re towing? I would have thought it would be the exact opposite - lower top speed when towing due to the higher vehicle weight, higher top speed when not towing due to lower vehicle weight and no concerns about the toad.

Just wondering.

[R Cabesa]

Then there is the right foot situation.



Comparing notes with a relative new owner next to me in camp a while back.



Both of us in E350/V10. Him just 3' longer with no toad. Me with 4000lb. Wrangler behind.


His jaw dropped when I said 8.5 towing and 9.75 not.



He said the best he had ever seen was 7.5.


It has got to be driving style and I'm no slow poke


An interesting note. I put 2-1/4" taller tires on which made the effective gear ratio about 3.84 with the stock 4.10 ratio in there. Way to high and my mileage went DOWN.



Regeared with 4.56 and an LSD. We do a lot of dirt road boondocking. My new ratio is effectively 4.36/1.



My mileage went back up!

[Ron Dittmer]

Originally Posted by AJMike

I just have to ask - why is your limiting speed when not towing lower than when you re towing? I would have thought it would be the exact opposite - lower top speed when towing due to the higher vehicle weight, higher top speed when not towing due to lower vehicle weight and no concerns about the toad.

Just wondering.

I expected the readers here would wonder about that.

That particular trip was the one time we decided to leave our tow vehicle home, and we had more time for a trip to slow down. I intentionally limited my top speed to 60mph to determine the best possible fuel economy our rig could achieve.

I have a ScanGauge-II installed on top of the center mirror (actually on top of our rear view display screen) of our 2007 E350 with V10 engine. When cruising on flat-open road at 60mph with no influential wind (grasses standing straight up) the readout consistently displayed around 13mpg fuel economy. But when considering every driving condition throughout the 5000 mile trip, the calculated average was 10.5mpg.

It is remarkable how often we drove into the wind. Then there were the many hills and mountains. Adding in some urban driving and some serious traffic. The trip encompassed good "all-around" driving conditions.

Compared to most other rigs built on an E-series chassis, our rig is quite aerodynamic, narrow side-to-side, and low-profile so it cuts through the wind quite well.

[AJMike]

Originally Posted by Ron Dittmer

It is remarkable how often we drove into the wind.

I have become convinced that when in our RV we are always driving into the wind. I think the existence of tail winds is a myth and the only winds that exist are either head winds or strongly buffeting winds from the side.

It does not matter if we turn around and go the other way. We still seem to run into head winds.

[Phil G.]

I didn't pay any attention to (potential) fuel mileage when we bought our Class C, new.

And I guess I was right about not paying any attention to fuel mileage then:

1) A few years ago it's transmission went South ... and the new (or remanufactured?) replacement cost was around $5600.

2) In addition, the insurance for it over it's lifetime has probably added up to considerably more than the dollars for the transmission incident.

I still don't care about fuel mileage ... the only cost I care about is the smiles per gallon it delivers.

(Of course I also care about CO2 in the upper atmosphere ... until Ford comes out with an electric E450 chassis. )

[checkthisout]

2 less cylinders with the new ford v8 vs the v10. It will get better mileage.

It also doesn't have to spin as fast to make the same horsepower. It takes fuel to make rpm.

Fuel mileage wise, my best guess is that it will equal the chev 6.0 but have better torque and generally better driving characteristics as would any big block vs small situation.

[VocalVirgo]

@UnclePaul, Thanks so much for taking the time to write this. I really appreciate it, and the info.