Why does my MPG gauge lie to me? - Ford Powerstroke Diesel Forum
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Old 02-11-2014, 04:37 PM
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Why does my MPG gauge lie to me?

My digital overhead MPG gauge says I get 18.4 MPG. But if I calculate it based on the trip meter and gallons of full used, I get 14 MPG. Why are they so far off? FYI the 14 MPG was city driving, I had a tank with 17 MPG highway. I'm hoping with the AIS intake upgrade I just did, the 4" exhaust that's on there and the addition of a chip, I can get some better mileage out of the beast.

The reason I ask is, if I get a Kiwi or other OBDII reader, will the MPG readings I get from it be wrong too? (i.e. be the same as my existing gauge?)

Last edited by MAArcher; 02-11-2014 at 04:43 PM. Reason: add question
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Old 02-11-2014, 04:45 PM
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you want to know my opinion?
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Old 02-11-2014, 05:06 PM
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Sure, what's your opinion?
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Old 02-11-2014, 05:08 PM
7.3 4 Ever! Nothing else!
 

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I drive a lifted 7.3L, I dont want to know what my MPG is LOL

if i knew, i think you will see a grown man cry hahahaha
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Old 02-11-2014, 05:46 PM
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I track my mpg.
But not because I care, I track it because a drastic change for no reason is an indication that there is a problem I need to address.
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Old 02-11-2014, 06:26 PM
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Sorry for hijacking your thread, but is their a way to actually track your MPG while going down the road?

Anybody heard of someone tapping their fuel line with a meter or something? That ways you can actually track how many gallons is used per mile on your trip meter.

Just a thought, maybe one of you engineers could come up with something like that.
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Old 02-12-2014, 01:41 AM
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Quote:
Originally Posted by peter379 View Post
Sorry for hijacking your thread, but is their a way to actually track your MPG while going down the road?

Anybody heard of someone tapping their fuel line with a meter or something? That ways you can actually track how many gallons is used per mile on your trip meter.

Just a thought, maybe one of you engineers could come up with something like that.
Mass flow meter. They are expensive though. Just bought one at work and cost 3 grand. Still needs to be calibrated as there is significant viscosity differences between fuel and water (aqueous solutions). Will post a link once I get to work. Not sure what the price difference would be for one that reads truck flow rate range.

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Old 02-12-2014, 03:11 AM
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The Torque app monitors your fuel flow. If somebody wrote a formula to factor in fuel flow with distance traveled (tracked by your GPS), you could get a fairly accurate reading.

My Lie -O- Meter has said anything from 10-11.5 mpg. Hand calculated, it's pretty consistent (without a load) around 15.2 mpg.
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Old 02-12-2014, 03:15 AM
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It's not that its mad at you, it's just disappointed.
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Old 02-12-2014, 04:35 AM
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Quote:
Originally Posted by AgTires4295 View Post
The Torque app monitors your fuel flow. If somebody wrote a formula to factor in fuel flow with distance traveled (tracked by your GPS), you could get a fairly accurate reading.

My Lie -O- Meter has said anything from 10-11.5 mpg. Hand calculated, it's pretty consistent (without a load) around 15.2 mpg.
Iirc, it uses icp and pw to calculate fuel flow. This is assuming a stock (cc/nozzle size) and healthy injection system.

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