There was some interesting chatter about "tweaking" the fuel gauge in this thread

 

The latest version of the Scangauge software has a speed correction, it works out to 5% for me and then the speed checks out against a GPS. I use that exclusively for speed these days.

The fuel left is an X-Gauge its the trip tank to empty for the fuel. I'm not sure how accurate it is yet, not very is my impression at the moment.

 

Ah, gotcha. I did notice my SGII speed reads about 1.5mph slower than my MINI. However, I went through one of those "Your Speed" traps a few days ago and when my speedo said 41 it said 37. Could've just been an inaccurate gun on the machine, though.

My parents have a GPS, I'll see if I can grab it to check it myself.

 

I remember reading an article years ago that came from GM about the fuel gauges not being accurate just like we are talking here. The then for a model year made an "accurate" gauge and received thousands of complaints that their vehicles were not getting the same milage there older GM cars got because the needle would more off Full quickly. They then went back to the inaccurate version the next year and have been there every since. Most car companies run this way in american cars for the preceived better milage. It would be interesting to see if Euro cars have the same issue.

 

The Euro cars I've owned (in the UK) had fuel gauges which worked pretty much the same behaviour. I always wonder why people make a fuss about this, all fuel gauges do this.

 

It's part of most cars programing. It's called fuel slosh. As the gas moves around in the fuel tank the manufactures programing to the instrument cluster dulls the signal - almost like a time delay - before the needle in the gauge moves. If they didn't do this as the gas emptied, the lower fuel level would create wild needle movements as the fuel moved front to rear left to right. Most pump assemblies have a small reservior to keep the fuel pump submurged and cool.

 

I had read on other thread on this same subject about how long you can go after the range says "0". That american drivers and maybe the UK also want a cusion of so that "E" dosen't really mean "E". The German drivers want to really know exactly how much fuel is in their tanks. My Mercedes is like that.It has a very accurate gauge.

 

I was bored and reading through this thread today. I was trying to visualize how these numbers would look on an analog needle fuel guage. Here's what I came up with:



DISCLAIMER: It's not really all that accurate or useful really. I don't even own a MINI [yet], just something I did in Paint and thought I'd share.

I got into a discussion with a friend of mine about this topic and though I was trying to defend the concept of a linear, or at least more accurate fuel gauge, his reasoning makes too much sense to ignore. Assuming a digital or analog fuel guage with say 4 markings that measures a 10 gallon capacity tank.

In a linear guage, the first marking would represent 2.5 gallons consumed and so would the space between that mark and each of the next ones. When you reach the last marking, representing that 7.5 gallons have been consumed and 2.5 gallons are remaining, you only know you have somewhere between 0 and 2.5 gallons of gas left.

In a non-linear guage, say the first marking isn't reached till an arbitrary number that seems too big for common sense, like 6.5 gallons being consumed, so you have between 0 and 3.5 gallons left. Then the second marking is at 7.5 gallons used (between 0 and 2.5 gallons left), the third at 8.5 (between 0 and 1.5 gallons left), and the fourth at 9.5 (between 0 and 0.5 gallons left. This would echo that behavior we see of it seeming like the needle goes down a lot slower for the first half of the tank than the last. But when you are at the last marking, you know that you have somewhere between 0 and 0.5 gallons left, compared to somewhere between 0 and 2.5 gallons for the linear guage.

Usually it matters more to know accurately how much gas when you are low on gas than when you have half a tank or more. So I guess the car manufacturers figure even if it's annoying for the first half tank, you'll be better informed as the car gets close to empty and less likely to run out on the road.