interesting MPG readings last two days

[DetroitDarin]

The insta-read is showing about 17.5 in town, and 19 crusing about 70. Prior to swapping from the 'Max Perf' tune, I was seeing about 17hwy.

MAYBE the tuner is simply re-programming the insta-read mpg to be wrong?

 

[FordandPolaris]

If you have a smart phone, there are many different apps that track MPG's accurately. I have an iPhone and use Gas Cubby. It would help verify the readings. Also if switching the tune reset the comp it might take a week or two for the reset fuel mileage to average out.

 

[DetroitDarin]

How can an App read my MPG? Sounds like sorcery.

 

[FordandPolaris]

Haha you input your mileage at the fill up as well as the amount of gallons it took to fill all the way up. It does some fancy math stuff (simple division really) and calculates it out. You have to remember to do it each fill up but I got in the habit quickly.

Sent from the Pocket Computer

 

[DetroitDarin]

Pic isn't showing for me -

The thing is, that only works if I know the speedometer is accurate. I can't prove that it is. If the speedometer is innacurate so will my miles-driven be off.

 

[FordandPolaris]

I also have bigger tires. GPS speedometer (another phone app) and some math shows I lose 1 mile for every 100 I actually drive. That is such a minimal difference the MPG's won't be too far off.

At 70 mph my speedo read about 3-4mph slow. Besides, the truck doesn't know you have bigger tires (unless it's in the tune?) and so the odometer in the truck will be just as accurate as the phone.


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[DetroitDarin]

but what is the margin of error in your GPS app?

 

[FordandPolaris]

Not sure, but like I said I checked the math too and it all was about the same. Unless your speedometer is incredibly off, it will all average out about the same. The difference is small enough to be negligible.


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[AskMeLater]

I use fuelly.com to keep track of my overall fuel mileage.

I use this bluetooth obd scanner http://smile.amazon.com/BAFX-Products-Bluetooth-diagnostics-Android/dp/B005NLQAHS/ref=sr_1_1?ie=UTF8&qid=1411180558&sr=8-1&keywords=bluetooth+obd2+scan+tool
with the Torque Pro app to check many vehicle functions, including instant MPG

Hope this helps