Quote:
Originally Posted by Old Mechanic
For the equasion to be correct the gallons used for each fill must be included, or you can use total miles and total gallons combined.
10 gallons 1300 miles @130 MPG
10 gallons 700 miles @ 70 MPG
2000 miles and 20 gallons is 100 MPG.
Am I missing something?
regards
Mech
edit, oops sorry red devil already covered it, long day today.
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When you have consistent tank fills, everything adds up nicely, but it works that way in
only that instance of exact same tank refills. It gets wonky when you try to add two different mpg readings for the same distance (or different distances).
The most common will be trip A to work, and trip B home: Both will be the same distance more or less but averaging the two will get you an inaccurate mpg number. For the same distance, The best you can do is double your worst trip. And even if you got 40mpg trip A uphill, and 1,000mpg trip B downhill, You'd get less than 80mpg combined. Which is why the lowest mpg you get matters so much. Trip B in this case is more or less a ratio between 0 and Infinite mpg of how much you can double trip A.
You need to think this way if your going to mentally calculate average section mpg. Say pulse 10meters(25mpg), coast 10meters(50mpg), coast 10meters coast 10 meters(75mpg).