NBtarheel33's Forum Comments

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Average price per gallon

IOW, a straight average price per gallon rather than a weighted average price per gallon. Gotcha. Interesting that the two are so close together, though I suppose that might be different if I had more partial fuel-ups.
posted by NBtarheel33 July 19, 2011 at 9:04 PM
Look at Little Bertha's page (the Saturn SL2). All-time gallons consumed is 3208.23, and all-time total spent is $8,530.78. So shouldn't the all-time average price per gallon be given by $8,530.78/3208.23 = $2.6590 = $2.66 to the nearest penny? And if so, why is the all-time average price per gallon under "Cost Analysis" showing $2.67?
posted by NBtarheel33 July 19, 2011 at 1:36 PM
And yes, I do have the profile pages set to "All-time".
posted by NBtarheel33 July 18, 2011 at 5:26 PM
This would be on the vehicle profile pages themselves.
posted by NBtarheel33 July 18, 2011 at 5:26 PM

Profile averages seem off

Why not calculate average miles per fuel-up as total miles tracked divided by n-1, where n is the number of reported fuel-ups? This would still throw out the first fuel-up, while simply incorporating "no mileage" fuel-ups as 0 miles (which is really what they are). Obviously, this will make the average miles per fuel-up lower, but the same sort of thing would happen even to someone who fueled up every 20 or 50 miles, right?
posted by NBtarheel33 February 10, 2011 at 8:02 PM
Actually, the two fuel-ups with the same odometer reading are legitimate distinct fuel-ups. I actually had run out of gas, so I had to put in just enough to get going again and limp under a mile to the nearest gas station to fill up the rest of the way. Turns out that the odometer reading was the same at the point where I had run out of gas and at the gas station. Is there a way around *that* kind of situation?

Also, with respect to overall average MPG, Fuelly shows 32.1 and I have 31.97. I'm guessing that this is due to the difference in averaging methods, or due to one or two fuel-ups being thrown out.
posted by NBtarheel33 February 10, 2011 at 9:49 AM

Recovering faster from partial fill-up

It is true that partial fill-ups sort of wreak havoc on the whole idea of tracking average distance between fuel-ups, and average cost of fuel-ups. What would be interesting (though labor-intensive) would be to compile a list of tank sizes for various vehicles (which actually, individuals can easily do, to get an idea of what's happening). If I know, for instance, that I am averaging 32 MPG all-time, and my tank is 12.2 gallons, I know that my average distance between fuel-ups should be 32 * 12.2, or 390.4 miles. Ditto for average cost per fuel-up, based on the average price per gallon. I have tracked my own mileage so carefully, that when the 2-gallon gas light comes on (and I know I have about 60 miles effective range), I have felt comfortable traveling up to 40-45 miles. Talk about freaking out your passengers!
posted by NBtarheel33 January 12, 2010 at 9:49 AM
Incidentally, I think we're missing the greater point here, to wit: 3+8 = 11, not 12. =P

Idea's still the same, but the numbers are uglier.
posted by NBtarheel33 January 11, 2010 at 8:36 AM
This is precisely how I deal with the "partial fill-up" problem in my own spreadsheet, and even go one step further, to avoid having blank entries:

You know that you went 210 miles on 12 gallons; that's 17.5 MPG. So, I go back and fill in the MPG for the 3-gallon "tank" with 17.5, and the 8-gallon "tank" with 17.5.

Now, I also like to track how different brands/octanes do over time. Obviously a partial fill-up messes things up here. But now I can go back and run the calculation, including 3 gallons of brand A at 17.5 mpg, and 8 gallons of brand B at 17.5 mpg. Obviously, it's not perfectly accurate, but it's close enough to get an idea of what's going on, and considering that I've only had three partial fill-ups in the last three years (precisely to avoid throwing my calculations off!), things smooth out nicely over time.
posted by NBtarheel33 January 11, 2010 at 8:34 AM

Bug - multiple fillups on the same day

Yep, that would be the ideal solution. In fact, I found that a way around this issue was to add times to my Excel spreadsheet before importing data, and then a 3pm fillup gets recorded before a 6pm fillup, for instance.
posted by NBtarheel33 February 16, 2009 at 3:42 AM