Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

2015 Subaru Impreza fuel indicator looks full

I am trying to understand a problem with my fuel indicator.After a fill up and driving a hundred miles or so the indicator stays on full.I just checked the fuel cap and found it was not clicked shut.
Now there is a bit of movement (one bar).
The dealer couldn’t explain what is happening.I hope it continues to function and am waiting to see before filling up again.
Perhaps understanding how the system works might help.

Bill H

Did you just acquire this vehicle ? Is this a new problem ? Do you have the dash read out for miles to empty and the other info about fuel usage ? I have had cars that the fuel level needle dropped like a rock at first and some that stayed on full for ever.

1 Like

The way it works is pretty simple. A float in the gas tank is attached to a swing arm. The arm is attached to a pivot with a rotary sensor of variable resistance. As the gas runs out, the float drops and the resistance changes. The gauge reads that resistance and shows the fuel level. It is very non-linear. Especially at full tanks.

1 Like

It is not at all unusual for gas gauges to stay at or near the full mark for many miles, and then to plummet rapidly. Car gas gauges are not laboratory-grade measuring devices, and only give you an approximation of the actual fuel level.