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Old Oct 8, 2013 | 09:12 PM
  #16  
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From: Lost In a Pit of Despair
Originally Posted by JWC 3
Well , If you are running it slapp out , marking miles and gallons ... Thats what you are gettin ! That my friend , is about as close as you can get .
I just thought it would be better

Oh well can't change it
 
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Old Oct 8, 2013 | 09:20 PM
  #17  
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Lol, you are in highschool driving an old *** truck...no matter mpg, that's cool as hell! In my day, 10-12 was average, so if you are getting that now, i would say you are doing ok. The greatest part about an old truck is that you can roll thru slow, and people still look your way😎
 
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Old Oct 8, 2013 | 09:25 PM
  #18  
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Originally Posted by jgavac
I just thought it would be better

Oh well can't change it
The method you have of checking your gallons used works ( too well for ones with only one tank ) ! Only thing left to ck , You odometer reading ! Is it accurate ?
 
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Old Oct 8, 2013 | 10:55 PM
  #19  
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These sixes were never that great in the mileage department but there are some decent tuning gurus in the engine threads here that have helped me immensely.
I have been getting much better mileage and power since I've been searching them.
 
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Old Oct 9, 2013 | 09:18 AM
  #20  
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How accurate is your speedometer? If it is off then your odometer will be off too. Check the speedometer with a GPS.
 
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Old Oct 9, 2013 | 03:54 PM
  #21  
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12-13 mpg may seem a little low for a 300/np435 combo, but you need to take into consideration you're driving a 3/4 ton 4x4 w/4.10's

The guys getting 16-20 mpg with a 300/np435 are most likely driving 1/2 ton 2wd's with more highway friendly gearing.
 
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Old Oct 9, 2013 | 04:18 PM
  #22  
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I have had Dents where the cab tank would take anywhere from 18 to 20.5 gallons, after running them dry. The readings can vary depending on whether the truck was running on the level or going up hill or down.
One gallon either way isn't going to make a huge difference in your mileage, but it will make some.

The only way to get an accurate mileage figure is actual miles divided by actual (not assumed) gallons, as many previous posters stated.

Also, as stated before, a F-250 with 4.10's is not a mileage oriented rig.

Another item to take into consideration is speedometer error. Is yours accurate?

Roger Carter
 
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Old Oct 10, 2013 | 06:30 PM
  #23  
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From: Lost In a Pit of Despair
Originally Posted by Roger Carter
I have had Dents where the cab tank would take anywhere from 18 to 20.5 gallons, after running them dry. The readings can vary depending on whether the truck was running on the level or going up hill or down.
One gallon either way isn't going to make a huge difference in your mileage, but it will make some.

The only way to get an accurate mileage figure is actual miles divided by actual (not assumed) gallons, as many previous posters stated.

Also, as stated before, a F-250 with 4.10's is not a mileage oriented rig.

Another item to take into consideration is speedometer error. Is yours accurate?

Roger Carter
I have been using actual gallons. All I was saying with the 19 is that is on average how much gas goes into the tank. Sometimes less, sometimes more.

I've been tracking my miles driven and comparing it to google maps and GPS readings. Over the past 4 trips, the odo has been off by less than .1 miles. So I think its safe to say the speedo/odo are accurate

Thanks
Jameson
 
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Old Oct 10, 2013 | 06:49 PM
  #24  
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Originally Posted by jgavac
As far as measuring, I fill up the cab tank (19 gal), mark the OD reading, and drive until I run out of gas and mark the OD reading again. Then I simply take the difference in the OD readings and divide by 19.
All of this speculation is useless because the way you're calculating mileage is wrong. There is no way around that. The tank is not at zero when you run out of gas, and it doesn't take 19 gallons to shut the pump off despite having a 19-gallon tank. You're assuming a differential of 19 each time, when in fact it is less than 19. This thread is a waste of your time until you calculate mileage as Mike described.
 
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Old Oct 10, 2013 | 06:55 PM
  #25  
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Originally Posted by jgavac
I have been using actual gallons. All I was saying with the 19 is that is on average how much gas goes into the tank. Sometimes less, sometimes more.
EDIT: guess I should have read your last post. Durrr.
 
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Old Oct 10, 2013 | 07:04 PM
  #26  
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Can I ask,what about the Octane level, would he get better MPG if he used a higher octane level? Often wondered that as don't they go by higher grade on newer Cars?

Allen
 
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Old Oct 10, 2013 | 07:08 PM
  #27  
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From: Lost In a Pit of Despair
I understand that it is not completely out of gas. I divide by however much it takes to fill it back up again, no matter what it is. I'm essentially doing what mike described. At least I think

Here the info off one of my receipts
Start mileage with full tank: 142,912.9
End mileage when I fill up again: 143,131.4
Distance traveled: 218.5 miles
Fill up with 19.023 gallons.
MPG: 218.5/19.023 = 11.486

-Jameson
 
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Old Oct 10, 2013 | 07:08 PM
  #28  
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Originally Posted by Az58Cameo
Can I ask,what about the Octane level, would he get better MPG if he used a higher octane level? Often wondered that as don't they go by higher grade on newer Cars?
The octane required by an engine is directly determined by its compression ratio. Mileage and octane have nothing to do with one another.
 
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Old Oct 10, 2013 | 07:32 PM
  #29  
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Originally Posted by Az58Cameo
Can I ask,what about the Octane level, would he get better MPG if he used a higher octane level? Often wondered that as don't they go by higher grade on newer Cars?

Allen
Octane (we use the AKI measurement method in the US) is a measure of a fuel's resistance to ignition. Octane does not indicate a fuel's purity, cleanliness, or energy content.
 
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Old Oct 10, 2013 | 07:56 PM
  #30  
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From: Lost In a Pit of Despair
Like Devin said, octane deals with resistance to detonation. Vehicles that have higher compression ratios require higher octane gas to prevent pre-ignition caused by compression. A lot of the newer cars that are turbo/supercharged require higher octane because of the turbo/blower adding pressure to the cylinders when the intake valves are open.
 
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