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Discussion Starter · #1 ·
Is there any way to make my Q5's (2015, "Progressiv" trim level, 3.0 V6 TDI) fuel gauge be accurate, or much more accurate than it is?

I fill my tank only until the pump stops the first time, so I do not overfill. I have an average range of about 1,180 km (~730 miles) until it's dry. The maximum fuel I've ever added was 74.29 liters, so I assume about 74.5 Liters is the usable fuel in the alleged 75 Liter tank.

My gauge is so inaccurate that after driving 200 km (~17% of tank), my gauge is still showing 100% full. Later, when I've consumed a calculated 2/3 of my usable fuel (1/3 remaining), the gauge shows a little less than 2/3 full. The gauge is obviously very nonlinear in relation to the actual fuel in the tank.
 

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In my experience all cars are different, some gauges show shed loads remaining for a few hundred miles then suddenly plummet, some the other way round, others are more linear. I think of them more as a rough guide than a definitive.
When mine gets into the red, regardless of mileage, I top up because I don't want to run the tank too low and risk sucking up any debris that might be lurking about the bottom.
I've never got remotely near 730 miles from a tank though, you're beating my best by over 300, don't think I've ever put in more than 65l mind you.
 

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Discussion Starter · #3 ·
SteveMcB: I too am using my fuel gauge as an extremely rough guideline. My low fuel light comes on at 120 km remaining range (~75 miles). I rarely fuel up without the range warning on. As you can tell, sometimes I've cut it pretty close.
 

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Mine does the "stay full" for 100+ miles; 1/2 tank between 300-350 miles then drops like a stone. I only get 500+ miles out of a tank about 50% of the time but there again I'm only getting to put 60-65 litres in; most of those times the light has been on for a while. Most I have ever put in is 69 litres; that was with the needle almost on the stop
 

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I manage to fill-up with 70 litres pretty constantly now. My range can actually increase after first 100 miles of driving before dropping. I just assumed it was because its using the fuel stored in the pipe leading to the tank, once that's used up it becomes more accurate. Might be completely wrong
I normally get about 650 miles per tank.
 

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Mine moves straight away 65litres with 50 miles in and it's under the full bar already.
I only get around 275-300 on a full tank.

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Mine moves straight away 65litres with 50 miles in and it's under the full bar already.
I only get around 275-300 on a full tank.

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Really? I get on average 570-600 per tank out of my SQ5.

The reason the guage does as it does is to do with the shape of the tank and where the sensor is located. The tank has a long neck which is why you see little movement initially
 

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Wow ????


That's a 60l full tank and done 137.9.

Why is it drinking twice as much as yours ????

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Probably because you are driving it like you stole it haha
 

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Yeah it is hard not to feel the torque every now and again.
What's the mileage on yours?

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Discussion Starter · #12 ·
...The reason the gauge does as it does is to do with the shape of the tank and where the sensor is located...
Actually, it's not the shape of the tank that's the problem, it's the type of fuel level sensor they're using, which I assume is a simple, linear, non-calibrated float sensor. The cheap and easy (and inaccurate) solution.

There are other kinds of sensors made, such as capacitive sensors, that can be accurately calibrated (or "mapped") to true fuel levels in the tank. With these types of sensors, you start with an empty tank of a known capacity (say 75 L, like the Q5), and take a reading. This reading maps to 0% on the gauge. You then add 1 liter of fuel and take a reading. This reading maps to 1L / 75L, or 1.33% on the gauge. Repeat adding 1 liter of fuel, taking a reading, and mapping, until you've reached the tank's full capacity.

Using this type of fuel level sensor and calibration technique, you could even have the strip run part-way up the filler pipe to account for those last few liters of fuel added before the pump clicks off. This would eliminate the "drove 200km while showing full" phenomenon.

This type of sensor, when correctly calibrated for your specific tank, gives you an very accurate true fuel level reading. You can even calibrate it to report usable fuel by starting with a fuel level that is barely accessible to the intake port of the fuel pump, and mapping that to 0% on the fuel gauge. I guess readers have not heard of this, and wouldn't know how to go about getting it or having it installed, calibrated, etc. I'm not a DIY sort of guy.
 
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