Partial Fill Screws Up MPG Calc... - Fuelly Forums

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Old 07-21-2020, 03:25 PM   #1
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Partial Fill Screws Up MPG Calc...

...once you get back to a filled tank.

Why does Fuelly add in the previous gallons of fuel but doesn't bother to add in the previous miles? This is flat-out stupid!

Partial Fill done on 6/26/20 with 312 miles driven and 7.695 gallons of gas.
Full Fill done on 6/29/20 with 181 miles driven and 13.837 gallons of gas.

Fuelly added the fuel together to get 21.532 and then calculated that amount of fuel used over ONLY the 181 miles for the full fill, resulting in 8.41MPG (and nothing entered for the previous fill).

I am completely confused at how the "math" for this site works and have always complained that two consecutive full fills were NOT necessary to calculate MPG so long as at least one full fill had been recorded somewhere in the past. Now I understand why two consecutive ones are required - it's because Fuelly isn't smart enough to track both miles AND fuel quantity as cumulative.

SMH
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Old 07-21-2020, 10:35 PM   #2
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I don't think you entered it properly, I saw the fuel up in question and the amount of fuel you put in on that fuel up is too high. Its even higher than some of your previous tank. A partial fuel up is when you don't fill the tank right to the top, example, you only put a gallon or two in because you want to use a cheaper filling station further down the road.
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Old 07-22-2020, 03:52 AM   #3
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Quote:
Originally Posted by Draigflag View Post
I don't think you entered it properly, I saw the fuel up in question and the amount of fuel you put in on that fuel up is too high. Its even higher than some of your previous tank. A partial fuel up is when you don't fill the tank right to the top, example, you only put a gallon or two in because you want to use a cheaper filling station further down the road.
I'm not sure how you reached that conclusion...

Full tank
Drive 312 miles (tank is close to empty), but only add 8 gallons, tank about half full.
Drive 181 miles, fill tank (close to 14 gallons).

The tank starts full. I drive a full tank's worth but only bring it back to half. This fill-up is marked partial and it calculates no MPG. Drive until tank is close to empty and completely fill.

Fuelly calculates the MPG using ALL of the gas added but only the most recent miles. If you add the fuel and miles together from the partial and the complete fill and average them, you get almost 23MPG which is roughly what would be expected.
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Old 07-22-2020, 06:11 AM   #4
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The 312 mile tank is the partial one, the one after, 181 miles, is a regular fuel up, you can't have gotten that much fuel in after a short distance. With method of tracking are you using?
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Old 07-22-2020, 06:21 AM   #5
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Originally Posted by Draigflag View Post
The 312 mile tank is the partial one, the one after, 181 miles, is a regular fuel up, you can't have gotten that much fuel in after a short distance. With method of tracking are you using?
The tank before wasn't full. So, yes, I absolutely could put that much fuel into the tank for the complete fill. Re-read my follow up post to understand the process...

I had a full tank and drove until almost empty. Partial fill. Drove until almost empty (which is going to be a much shorter distance since I wasn't starting with a full tank). Filled the tank.

I track by odometer.
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Old 07-22-2020, 09:04 AM   #6
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Previous partial fills were calculated correctly.
This is probably a bug that came up with a recent update.
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Old 07-22-2020, 09:08 AM   #7
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Originally Posted by trollbait View Post
Previous partial fills were calculated correctly.
This is probably a bug that came up with a recent update.
Yes, I did notice that a previous partial and complete fill combo did seem to calculate correctly. Are the calculated values stored and retrieved when viewing a page? Why aren't they calculated each time? I would think that partial/full fill combos would be either all correct or all incorrect.
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Old 10-13-2020, 12:52 AM   #8
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Hmm, I wonder if OP was already able to solve this.
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Old 10-13-2020, 04:42 AM   #9
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Hmm, I wonder if OP was already able to solve this.
It really isn't my problem to fix...
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