How accurate is the fuel gauge on a Xantia?

[Napoleon]

Any Xantia, I mean (unless there is a marked difference between them, that is).

I want to be able to calculate fuel consumption properly, bot trying to guess within 10l how much fuel has been used by looking at the gauge.

Ta.

[rory_perrett]

In my experience of 3 different Xantias, not accurate at all (in a scientific sense). Firstly it is not linear, full to 3/4 represents a different amount of fuel used than 1/2 to 1/4. The reading it gives depends on battery voltage, mine reads higher first thing in the morning than it did at the end of the previous day. At the top end, you can still get a significant amount of fuel in after the gauge shows full.

There is also a difference between cars, current car takes 63 ltrs when the light comes on, previous one would only take 58. Having said all that on the same car if you were to use the same point, like the fuel light coming on, you will get a fairly good figure.

I usually fill the tank each time and use a calculated rolling weighted average over 5 fills.

[Xaccers]

About as accurate as using the engine to gauge if you have fuel or not (ie if it's running you have fuel, if it's not then you're empty).
Fill it up, reset your odometer, go for a drive, fill up and work out how much you used and how far you travelled.

[CitroJim]

In my experience of 3 different Xantias, not accurate at all (in a scientific sense). Firstly it is not linear, full to 3/4 represents a different amount of fuel used than 1/2 to 1/4. The reading it gives depends on battery voltage, mine reads higher first thing in the morning than it did at the end of the previous day. At the top end, you can still get a significant amount of fuel in after the gauge shows full.

Sounds like my cars Rory They're all different. The HDi stays at apparently full for ages, then flies down to half, stays there for ever and then when it begins to move down a bit from half I fill it. The Activa seems the best of the lot and is fairly linear and accurate. The V6 is well, good for predicting earthquakes but little else. It never reads truly full and is basically pessimistic in all areas. It indicates the presence of fuel in the tank and little else...

So there you have it - three Xantias and all behave differently fuel-gauge-wise

The Activa, I believe, has had a new sender fitted in the not too distant past.

[Sulla]

The 2 Xantia's I have owned also had wildly behaving fuel gaugues. The 1.9Td used to fall through the first half quite steadily and then take an age to go from half full to the light on. The HDi will stay showing full for in excess of 200 miles then drop fairly steadily to 1/4 full, after this the last quarter tank goes within 30-50 miles depending on urban or extra urban. I know from experience that when the gaugue is showing 3/4 full it has used around 29-30 litres.

As these guys have said, the only way to measure fuel use is to brim the tank, drive a bit and then brim it again, sit down and calculate.

[Napoleon]

Cheer chaps, suggestions welcomed. (only one that is easy, anyway).

[Stepto1]

I don't trust any gauges on my Xantia HDI.

I know the speedo and odometer are out by nearly 10%

The fuel gauge stays at full for about 150 miles then drops to about half and stays there.

I recently took a series of temperature readings from different places around the engine. The temperature gauge was nowhere even close. It read much lower then then even the coolest part of the engine.

I gues the rev counter may be correct!

[CitroJim]

I gues the rev counter may be correct!

I wouldn't bank on it

[jgra1]

my gauge definitely seems logarithmic.. the more fuel I use the quicker it moves.. i.e. stays 'full' for a long way.. the upper half takes reasonable time to go down, the latter half quick..

[Old-Guy]

As these guys have said, the only way to measure fuel use is to brim the tank, drive a bit and then brim it again, sit down and calculate.

It's important to fill at the same pump (facing the same way) each time; forecourts often slope gently and even a slight slope can make a significant difference to the amount of fuel the tank will take.

[Mandrake]

Sounds like my cars Rory They're all different. The HDi stays at apparently full for ages, then flies down to half, stays there for ever and then when it begins to move down a bit from half I fill it. The Activa seems the best of the lot and is fairly linear and accurate. The V6 is well, good for predicting earthquakes but little else. It never reads truly full and is basically pessimistic in all areas. It indicates the presence of fuel in the tank and little else...

Sounds just like my V6 - it never reads full (only goes up to about 80%) but stays on that 80% for a long time, reads half when its got less than half in it (estimated based on mileage) and then drops rapidly below that. The low fuel light is supposed to come on with 8 litres left according to the book but last time I filled up when the light came on I could only put 52 litres into a 65 litre tank.

My 2 litre petrol had a lot more linear gauge from what I can remember, and it did go to full scale accurately, but I would never use the low petrol light or the gauge to estimate fuel consumption, brimming the tank is the only way.

For starters the fuel sender is heavily affected by body roll - park sideways on even a small slope and it will either read too little or too much petrol depending on whether the car is leaning to the left or the right. I frequently get the low fuel light coming on when I leave work because I park on a slight sideways slope, but then if I turn off and on again at home on the level it goes out again.

Both the low petrol light and the gauge itself have a very slow moving average system to make it deliberately slow to respond to changes in fuel level - otherwise the reading would be going up and down every time you cornered...(turning the key off and on resets it quickly to give a correct reading after filling up)

[Northern_Mike]

Any Xantia, I mean (unless there is a marked difference between them, that is).

I want to be able to calculate fuel consumption properly, bot trying to guess within 10l how much fuel has been used by looking at the gauge.

Ta.

In my experience, they are useful for telling you there is "some" or "some more" fuel in the tank, and not a lot else..

[Grayone]

Having had just one Xantia, an X reg 2.0Hdi SX Estate since 2002, my experience is limited but I do agree with others. Don't trust the gauge, it's not inaccurate just not linear. My method is to brim the tank, drive to the reserve light then brim again. After a while the odometer gives the best measure of how far you can go. Being anally retentive I keep records on Excel and have done on all my cars for some years

[Chris570]

Any Xantia, I mean (unless there is a marked difference between them, that is).

I want to be able to calculate fuel consumption properly, bot trying to guess within 10l how much fuel has been used by looking at the gauge.

Ta.

In my experience, they are useful for telling you there is "some" or "some more" fuel in the tank, and not a lot else..

That's about it, the light isnt exactly brilliant either