Originally Posted By: Garak
Originally Posted By: virginoil
It is possible to measure mpg down to 0.2, I have done so for many weeks when I choose to measure the mpg.
How do you account for the pump's inherent accuracy not even being that good? I know up here, they're allowed to be out up to 5%, depending upon the direction, despite the fact that they tell us volume down to the nearest millilitre. By nominal significant figures, it's relatively easy to go to four significant figures, but that involves ignoring a lot of reality about the errors in our measurement.
I fill at the same fuel pump, fill to the first click on the fuel pump, record the litres to fill the tank,measure the kilometers and then calculate the mpg or L/km.
I usually drive the same route and in similar traffic conditions another factor.
However, the calculations are usually with +- 0.2mpg and these are consistent and on vehicle that gets 23mpg it is within 2% band and the tolerances in readings are good enough for my purposes.
It is ridiculous to mention 4 significant figures as it appears all the potential errors cancel out if you use the same pump each week.
Originally Posted By: kschachn
Originally Posted By: virginoil
It is possible to measure mpg down to 0.2, I have done so for many weeks when I choose to measure the mpg.
If all things being equal and the only change was the switching of the oil brands for a season and the mpg went back to normal after the switch back to the usual oil brand then the OPs claims are valid, and you don't need a LAB to confirm the result.
That is not correct. .........................................................
The isolation of variables becomes more difficult but more important as the variable effect gets smaller. The wide noise band (as Garak notes) of real-world driving masks a lot.
Sober up please, the consistency in the results are good enough for me in real world conditions.