I've compiled a mostly accurate chart, though it does not have any error bars. Error comes from two places:

In reading the gas gauge, it is marked in 1/16 increments - therefore, the error associated with the position reading is 1/32.

In filling the tank up, it's a bit more complicated. To reduce error, I always let the pump stop by it's own, and fill up to the next 1/4 dollar. That way, it mostly should even out any error there. I don't have a figure for that number, but it's probably around .1 ~ .25 of a gallon.

In the lower portion of the gauge it seems a bit linear. The next few weeks I am going to test the upper portion of the gauge, to see if that's a bit more erratic, as it needs to curve down to meet [1,0].

 

 

Ah yes, good question . Basically, my previous vehicle would always go for 100 or even 200 miles before the gas gauge dipped down. I noticed this to a lesser extent in the MINI, but I can go about 40 miles (roughly 1.5 gallons) before the gas gauge dips down - I figured in this modern day and age the gauge would be a bit more accurate. So... I created a calibration curve to see if if was just a bit more linear.

I mean, it ain't scientific, but it surely fits in this area of NAM.

 

Interesting...

I imagine that it's totally within the capabilities of engineers to design a completely linear fuel gauge, pure speculation but theres probably some studied psycological reason for having it work this way, like people don't run out of gas as much if it operates like this.

Along the same lines is the temperture gauge which once warm always displays the same needle position even if the engine becomes slightly warmer or cooler.

Erik

 

The gas gauge has always gotten on my nerves. I like to estimate my total mileage for a tank at the half way mark, but my gauge acts like it is exponential.
The first half a tank will see 200+ miles. The last half will see 100 to 130 miles. The needle just starts accelerating from 1/3 a tank to empty.

I've been meaning to chart out the gauge/sending unit/actual gas/mileage and see if I can fix this for a while. Maybe this thread will motivate me.

 

One of the things I've really noticed about the Mini is how non-linear the fuel gauge is, particularly once the needle passes the half-way point. I just completed a trip from Chicago to Cleveland and back. At the midpoint, adding the range to the miles traveled (zero'ed out at fill up)indicated that I should have made over 400 miles on a tank. In actuality, I only made about 330 miles.