I brimmed my tank yesterday, and the needle sat bang on the maximum notch on the gauge, just as expected. However, on traveling 42 miles (for the sake of argument, roughly a gallon of fuel) the gauge as can be seen has dipped quite alot. I've done MPG tests in the past and 35mpg was average. Is the fuel gauge just horribly pessimistic?

On a Mk7 Fiesta, quite accurate it seems!

i dont know about your car but they can vary a bit due to the uneven shape of the tank. Eg if a tank is narrower at the top then the float will go down quicker when in that region of the tank. And are you on a hill, that affects it also

5 minutes ago, isetta said:

i dont know about your car but they can vary a bit due to the uneven shape of the tank. Eg if a tank is narrower at the top then the float will go down quicker when in that region of the tank. And are you on a hill, that affects it also

No hill, but out of interest grabbed a photo of a Focus petrol tank, and it looks fairly rectangular. Just surprised that even after 10 miles you can see the needle shift significantly. I hired a VW Golf last year and honesty the needle barely budged after 50 odd miles! I even have a GT4 which drinks petrol and the fuel gauge doesn't appear to move as quickly. Just thought that with such a relatively frugal car, it would show 'full' for longer LOL

 

 

 

I can go over 30 miles before the "full" readout on the needle starts to go down.

Just be glad it isnt a 2004 1.1 Kia Picanto, you could do 100 miles on that with a full read out and then suddenly the needle would drop like a stone!!

Cars do have a habit regardless of model of showing more miles 'at full' due to the way they shape the tanks and where the actual sensor starts.

In some cars, turning left or right depending on the car/make/model would give a brief lower/increase in fuel on the readout gauge due to the way the fuel sloshes to one side during a corner.

It would look like your gauge is actually more accurate than the ones that dont move for ages.

on my fiesta it does not move until I have done about 50 miles from a fill up. In my nearly 40 years of driving I would say most cars I have owned have a fuel guage that moves down slowly in the top half and moves down more rapidly in the bottom half. I have not owned a focus mk2

On the Golf I can do around 85 miles before it moves off the max marker.  I've currently done 100 miles on 1/16th of a tank...  

It drops suddenly for the last 100 miles though, so much so that I can't trust the range or the gauge towards the bottom, I just work on the amount of miles I've covered instead, I know I can get 600 miles to a tank.  I reckon a previous owner has just filled up a tenner at a time and worn the bottom end of the gauge.

I found the gauge on the Mk2.5 Focus to be fairy accurate tbh, a lot more accurate than the Mk3 gauge anyway!  

My 2.5 was on 80 miles one day and I parked in a car park on a slope to go shopping. When we got back and drove off it was on 90 miles and continued to drop at that level so not very accurate lol

The fuel guage relies on a simple float like the ballcock in a toilet...  If you park on a hill it will of course be inaccurate!

 

I have no idea how my gauge moves tbh, I always fill up when the computer says about 75 miles left!

18 hours ago, F0CUE said:

My 2.5 was on 80 miles one day and I parked in a car park on a slope to go shopping. When we got back and drove off it was on 90 miles and continued to drop at that level so not very accurate lol

Are you saying someone went on a 10 mile joyride in your absence? LOL

Nope the opposite they put some in instead lol

I've found the best way to get my needle to move is to floor it in 3rd! There's nothing 'eco' about overboost!

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On 1/19/2019 at 10:36 PM, dtulip8 said:

I have no idea how my gauge moves tbh, I always fill up when the computer says about 75 miles left!

You shouldnt worry the sensor always stops before the actual level of fuel in your tank becomes empty, its a fail safe (In terms of stopping the manufacturer being sued fail safe, ie no one can say "my gauge still said I had fuel" when they run out). Most cases you still get another 20 miles of fuel when it hits 0 on the readout, impossible to find a fuel station in Britain that'll be more than 20 miles away. I've once rolled up to a petrol station with 0 miles on the clock.