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Old 08-01-2020, 08:25 AM   #1
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Same exact class C/different engine miles per gallon

So Iím sure these questions have been asked, but maybe not quite in the same way. There are a few class C motorhome is now available that have exactly the same set up, tank sizes, dimensions, shape, and for all intents and purposes- weight on the back of two different cutaway chassis with two different engines.

So for example, if you wanted a Caoachmen Freelander with the Chevy 6.0 6 speed automatic, And you compared it to the same coachman free lander on the new Ford 7.3 also with a six speed automaticÖ Aside from obvious power differences, which one is going to deliver better gas mileage?

I ask because coachman offers their smallest unit, at 24 feet long, with a choice of either chassis/engine setup. I would think that a coach that small would benefit from having a bit of a smaller engine from the ChevyÖ But maybe the fuel management system is more advanced on the much larger Ford engine. I really canít find a fair comparison online, not even pick up truck to pick up truck because the 6.0 hasnít been in Chevy/GMC line of pick up trucks in many years.

Keep in mind, the only weight difference in both of these identical coaches would be the difference in weight starting with the original stripped down cut away chassis that it is built on. But thatís it. Everything else, weights/dimensions/capacities are the same. And yes, I am aware that the Chevy has a 57 gallon gas tank and the Ford has a 55 gallon gas tank. But that, And the cutaway chassis weight differences are the only differences.

Any thoughts or info?
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Old 08-01-2020, 10:35 AM   #2
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Neither one will get anything to brag about. If you are sweating tenths of an mpg, RVing is going to be a miserable experience. I would focus on the unit that had enough power to handle your payload over your preferred terrain and its dependability to get you there. Enjoy the trip, the gas card won't be in the mailbox till the next month.
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Old 08-01-2020, 10:43 AM   #3
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Any minimal difference in mpg between the two would not be worth worrying about. It's is a motorhome, after all.
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Old 08-01-2020, 02:34 PM   #4
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While the easy answer is all fuel economy in an RV is bad so you don't purchase an RV for fuel economy, doesn't really address the issue. I to have been wondering about the 7.3L Ford vs the Chevy...and actually vs the Sprinter. The problem is that the 7.3 is so new that there is no real world feedback. Will it match the V-10 or will it improve to at least the Chevy? From prior posts the V-10 averaging 6 to 8 mpg - but a lot of Class A's also reporting. Chevy averaging 9 to 11. While all nothing to brag about, the Chevy had a 15 to 25% over the V-10. Now if the 7.3 matched the Chevy, but had the performance increase, it would really be interesting.

Now take it a step further with the Sprinter which typically averages 15mpg. Obviously, neither are going to approach that...or will it if you change the question from mpg to cost per mile equivalent OVER THE SAME DISTANCE. Currently, unleaded locally is $2.05 and diesel is $2.69, or 30% higher. Now equalize for the same fuel budget. 10 to 11 mpg of the Chevy plus the 30% fuel cost difference would be 13 to 14.3 which would make it very competitive with diesel 15mpg. But the V-10 doesn't stand a chance with a 7.8 to 10.4 mpg equivalent.

So the question remains...just where does the 7.3L stand? Frankly, I am leaning towards the Chevy, but open to the Ford as both have more power than the Mercedes and far better CCC. Ford has to convince me though.
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Old 08-01-2020, 02:55 PM   #5
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It takes X amount of HP to move a RV down the highway.

You need X amount of fuel to create X amount of HP, no matter who built the engine.

The loss in economy will happen when you call for more power while taking off or climbing hills.

That, you cintrol, with your foot on the gas pedal.
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Old 08-01-2020, 03:59 PM   #6
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You don't buy an RV to get good gas mileage. The MPG you get will depend on how fast you drive and where you drive.

Overall it takes a fixed amount of HP to move the rig of a certain weight down the road at a given speed. The engine needs a fixed amount of power to accomplish this. To get this HP it requires a certain volume of gasoline.

The 6.0L GM engine will develop its power at a higher RPM than the 7.3L Ford engine. The Ford engine was developed as a truck engine and will have more torque at lower speeds.

A fixed volume of gasoline has a fixed heat content or available power. The difference in engine efficiency will be petty minimal and both engines will produce the power, so you will not see much difference in fuel usage over all.
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Old 08-01-2020, 06:36 PM   #7
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An RV is heavy and a huge block with not much wind cutting... Atleast many big rigs today have the technology edge to move thru Air (still a box) but motors have evolved and are dialed in with transmission so a 80000 load on the open road is getting better MPG than most RV.s..

The New ford 7.3 vs the Chev 6.0.. A lower RPM vs A higher RPM,.. normally when moving a load cubic inches or litres make the deal.. Voluemetric efficency of a bore/stroke combo can even the playing field at cruise and even make MPG better,, but once your foot needs to be in it,,, MPG is a fantasy.. Your are back to extracting X power from X fuel ...

Back in the Day I had a K5 Blazer, 410 rear 30in tires.. 350 4V. 11-12 MPG, no mater what..
I did a project and built a 250 inline 6 to a tune of 260hp..at 6200 rpm.. The 350 was rated at 250 at like 4500..
The Six was a fun project BUT it still got 12mpg.. maybe 12.6..
I remember talking with Crane Cams about a grind that would give MPG.. they said NOPE it is a block dragging down road, we could help you dial in the motor if you put in a camaro etc.. you may get 16-18 but not the power..

Blah
blah

Like said RVers should not worry about MPG.. it is about the fun and upgrades and tinkering and sitting by a fire, or just R&R on a lake...
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Old 08-01-2020, 08:04 PM   #8
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Quote:
Originally Posted by tizeye View Post
While the easy answer is all fuel economy in an RV is bad so you don't purchase an RV for fuel economy, doesn't really address the issue. I to have been wondering about the 7.3L Ford vs the Chevy...and actually vs the Sprinter. The problem is that the 7.3 is so new that there is no real world feedback. Will it match the V-10 or will it improve to at least the Chevy? From prior posts the V-10 averaging 6 to 8 mpg - but a lot of Class A's also reporting. Chevy averaging 9 to 11. While all nothing to brag about, the Chevy had a 15 to 25% over the V-10. Now if the 7.3 matched the Chevy, but had the performance increase, it would really be interesting.

Now take it a step further with the Sprinter which typically averages 15mpg. Obviously, neither are going to approach that...or will it if you change the question from mpg to cost per mile equivalent OVER THE SAME DISTANCE. Currently, unleaded locally is $2.05 and diesel is $2.69, or 30% higher. Now equalize for the same fuel budget. 10 to 11 mpg of the Chevy plus the 30% fuel cost difference would be 13 to 14.3 which would make it very competitive with diesel 15mpg. But the V-10 doesn't stand a chance with a 7.8 to 10.4 mpg equivalent.

So the question remains...just where does the 7.3L stand? Frankly, I am leaning towards the Chevy, but open to the Ford as both have more power than the Mercedes and far better CCC. Ford has to convince me though.
Really good comparison of the 6.0 and the new 7.3. Wouldnít that be great if orders able to match that little bit of better gas mileage than the 6.0 makes, but you have tons of extra power....
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Old 08-02-2020, 07:21 AM   #9
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Really good comparison of the 6.0 and the new 7.3. Wouldn’t that be great if orders able to match that little bit of better gas mileage than the 6.0 makes, but you have tons of extra power....
The question is if despite the 'disadvantage' of the larger block creating more horsepower, can the advantage of creating that power at lower RPM on the power curve than the relatively high RPM level of the Chevy create competitive mpg performance? The V-10, despite referred to as bulletproof, is known as a screamer developing the necessary power at higher RPMs to perform as expected. All the more reason we need real world feedback on the 7.3 engine. That may be the positive impact of the current retail environment where dealers don't have the inventory and where incoming are snapped up enroute or within a week of arrival. Unless have to place order now which would require an immediate decision for later delivery, or need an RV now and snap up incoming, can wait 6 months or so for inventory build-up and potentially have the performance feedback from current purchases.
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Old 08-02-2020, 08:01 AM   #10
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Quote:
Originally Posted by tizeye View Post
The question is if despite the 'disadvantage' of the larger block creating more horsepower, can the advantage of creating that power at lower RPM on the power curve than the relatively high RPM level of the Chevy create competitive mpg performance? The V-10, despite referred to as bulletproof, is known as a screamer developing the necessary power at higher RPMs to perform as expected. All the more reason we need real world feedback on the 7.3 engine. That may be the positive impact of the current retail environment where dealers don't have the inventory and where incoming are snapped up enroute or within a week of arrival. Unless have to place order now which would require an immediate decision for later delivery, or need an RV now and snap up incoming, can wait 6 months or so for inventory build-up and potentially have the performance feedback from current purchases.
Perfectly said. We wonít know until new owners start to share their feedback.
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Old 08-02-2020, 08:38 AM   #11
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Originally Posted by L.C.Gray View Post
Neither one will get anything to brag about. If you are sweating tenths of an mpg, RVing is going to be a miserable experience. I would focus on the unit that had enough power to handle your payload over your preferred terrain and its dependability to get you there. Enjoy the trip, the gas card won't be in the mailbox till the next month.
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Your mileage will be between 7-9 on both units. Look hard at layout of rig. If you plan on towing a car then do yourself a a favor and get the larger engine. You will need it in the mountain states regardless of rig length. If you drive 10,000. Miles a year that comes out to around $800 in additional gas cost. If you can’t afford that for the better performance don’t get into rving. It will break you.

Enjoy the journey
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