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Old 04-16-2021, 01:18 PM   #1
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UPDATE : My True MPG 7.3L V-8 Gas

After 2 months fixing my motorhome of the issues and installing new stuff when it was bought new in February this year I decided to learn the instrument panel settings and found things I did not know I had.

1st off most my driving in the past 2 months have been some highway and mostly around town and my average mpg was around 8.6, also the average mpg the day I bought it was 8.2 and has only slowly gone up.

Well I found out I could clear that average reading and also found out I also have exact mpg reading while driving.

So I cleared the settings and went on a drive for 30 miles on highway and about 7 miles in town and by my surprise I have been getting far better mpg than I have posted on here before.

At 60 mph cruise control set mostly flat highway no wind I am getting around 12-13 mpg on the flat areas as to Fords display on instrument panel and now my average after driving for about 7 miles in town after the highway drive I am getting 11.5 mpg

So the new Ford 7.3L gas V-8 is getting good mpg and this has me even more happy staying with the big block V-8 vs the small block V-6 in the other small Class B+.

However this is just a short run test, I will be going on a long 1000+ mile trip very soon and will let you know the true long run mpg.

I wished I had learn the settings when I 1st bought it but been busy doing other things..

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Old 04-16-2021, 03:52 PM   #2
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I have found that the in dash MPG displays are about 10% off on the high side.

Ken
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Old 04-17-2021, 05:09 AM   #3
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The only real way to know your true MPG is to manually calculate it. Once you do this you will know how accurate the Ford displayed numbers are. Your 1000 mile trip will be a great time to do this. I use an app on my phone to track MPG and other expenses.
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Old 04-17-2021, 05:35 AM   #4
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I have found that the in dash MPG displays are about 10% off on the high side.

Ken
Long term ( 6 months or more) my 2 ford vehicle are accurate, if they are reset short term the are off ( short term is under 5K miles )
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Old 04-17-2021, 05:35 AM   #5
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The only real way to know your true MPG is to manually calculate it. Once you do this you will know how accurate the Ford displayed numbers are. Your 1000 mile trip will be a great time to do this. I use an app on my phone to track MPG and other expenses.
Calculating your MPG “manually” is complicated by the fact that the generator pulls from the same tank. You can use generator hours to estimate its fuel consumption but, since you can’t know the load, and thus actual generator consumption, it’s just a guess.

I think the new vehicle computers are very accurate. They give you the exact fuel flow to the engine only, both instantaneous and over time.
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Old 04-17-2021, 06:00 AM   #6
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If manually calculating, you need a significant distance to get accuracy. Calculating for a single tank fill up (for instance, knowing that you drove X miles on the last tank, and then "filled up" with some gallons, then Y miles on the next tank, and "filled up") assumes that the pump's notion of "full" is the same for every pump, which isn't the case. There's some variation in when pumps will automatically stop. Over a thousand miles or so, that will come out in the wash.
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Old 04-17-2021, 10:30 AM   #7
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I have found that the in dash MPG displays are about 10% off on the high side.

Ken
Yea I am thinking they may not be accurate so on my trip I am going to use the old fashion test filling up and writing down the mileage and checking at the next fill up.

Unlike my class A I sold I could see the gas gauge move and the gas gauge on the class B+ stays in place for sometime.
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Old 04-17-2021, 10:43 AM   #8
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I have an Excel spreadsheet that I use to track the mileage for every vehicle I have. My motorhome, now sold, it even in there. There are different tabs for each vehicle. I started this in 2011 when I bought a car that was difficult to fill and get consistent numbers from.

My Winnebago View 23H motor home on a 5 cylinder Sprinter chassis, averaged 17.008 MPG over 53 refuelings and 13,261 miles for a cost of $1985.03 and a per mile cost of 14.9 cents.

The spreadsheet also allows me to keep track of WHERE the vehicle was refueled each time so I can see if a particular station's gas gives me better or worse mileage (yes, there is one that stands out) and also it gives me a record should I have any fuel issues.

Also, I generally "pack" the tank, by at least running up to the next dollar, possibly two dollars. On some gas vehicles this can cause issues, and mileage losses should it flood the carbon canister in the vent, but both of my gas vehicles have canisters that are high enough that this is not possible and I have never had a problem doing this. It helps provide consistency to the refuelings.

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Old 04-17-2021, 07:21 PM   #9
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On reason why the dash can read better than your true mileage is if the computer integrates samples over time instead of distance. For example: Lets say you drive an hour at 30 MPH, and you get 12 MPG for that hour. Then you drive another hour at 60 MPH, and you get 8 MPG during that section of the trip. Averaging those based on time gives you 10 MPG (1 hour total in each sample). Even if it grabs a sample every minute, you have 60 samples in each trip segment, so still you have (60 * 8 + 60 * 12) / 120 = 10 MPG.


But in reality you drove 90 miles, using 10 gallons, which comes out to be 9 MPG. So there is your 10% difference in what the display shows.
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Old 04-18-2021, 12:43 PM   #10
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I have found that the in dash MPG displays are about 10% off on the high side.

Ken
They almost always read better than actual. If you only use the OEM mpg gauge, your kidding yourself. I also include generator usage because that is what you are putting in the tank.
I learned the correct way to drive for economy. My 35k lbs Diesel pusher gets 8.8 My C Class gets 9.8, including minor Gen usage. I get about 20-30% better than most.
55 mph, slow down uphill, speed up downhill, hold a steady foot NOT speed.
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Old 04-28-2021, 11:47 AM   #11
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Well just got back from a long trip well over 1000 miles and my average gas mpg reading on the Ford dash display reads 11.9 mpg.

Did check from fill up to fill up and read the miles driven and on that one leg of the trip it showed 11.3 mpg while the Ford display reading was 11.5 mpg on that leg of the trip, so it appears the display on dash is very close to actual miles.
[ no generator use at all on trip, no need for a A/C ]

I am very pleased with the mpg on the Ford 7.3L gas V-8, at 64 mph flat road no wind it reads 12-14 mpg, lots of extra power even in the mountains in Idaho and stayed in 6th gear almost all the time, never had to push the gas pedal beyond half.

Ford got this motor and transmission combo perfect, best I have even owned.
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Old 04-28-2021, 01:39 PM   #12
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Ford got this motor and transmission combo perfect, best I have even owned.
Best I have ever owned..

Why does edit go away after a hour or so ??
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Old 04-28-2021, 01:54 PM   #13
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Always more interested in actual miles driven (ya, needs to be close to what your GPS says) against total gallons over those 1,000+ mile trips.


Too many experiences with WOW pulling in to fill up and WOW, that is a lot less as I leave.


Optimism has its place, but not in calculating MPG.
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Old 04-28-2021, 02:30 PM   #14
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The only real way to know your true MPG is to manually calculate it. Once you do this you will know how accurate the Ford displayed numbers are.
Well, yes and no, at least IMHO.

Filling up at different stations means using different fuel pumps, and the automatic cutoff on different pumps work differently. Some pumps cut off too early, giving you the impression that you have gotten high mpg figures than are accurate, and then the next fill up is likely to show a lower figure. And neither of those figures are likely to be accurate. I believe that is even true when you don't accept the automatic cutoff as being the final word and add more fuel.

It has been my experience that computing the figure using the miles and gallons works properly only when a lot of miles and a lot of fill up are involved, and that is why I only use those figures at the end of a relatively long trip - say 2000 miles - or after a lot of fill ups, perhaps 10. Then I assume the multiple figures will average out to something fairly accurate.

FWIW I have found the mileage figure the Ford Transit 350 HD chassis gives me in my Winnebago Fuse is pretty accurate, usually no more than 0.5 - 1.0 mpg off at the most and I have come to believe it.
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