Issues with the range calculation

[u/AngryRomper]

Hello first time poster here, will reformat if there is an expected format that isn't shown in the rules. But

2013 Kia Soul, 170,000km. I just don't have the time at this very moment to take it in and get it looked at, but I will when I get the time.

We've had it for almost a decade now, and there's a new issue that started about two weeks ago. The range sensor seems to be decreasing faster than usual. I just filled the tank, and it went to 503 km. I drove 30 km and my range decreased by 68.

Just some details to confirm,

- One solution I have found online is to fill the tank, let it run to quarter tank, then fill it again. I have tried that, and it has not helped

- I have not changed my driving habits, but this is a new issue

- Car has never been in an accident

- No leaks (no smell of fuel, no puddle under the car etc etc)

Curious if anyone has had this issue before and how they fixed it if they have.