Fuel gauge problems - both digital and analog

Hello! I have a 2000 Buick Regal, LSE edition, 3.8L V6. My fuel gauges have been acting up lately.

The analog gauge fluctuates by about 1/4 of a tank. For example, if I have just filled up the car, it should be on full. But when I start the car, the needle will not be on full and will start out showing much less gas than I actually have. So when I first start the car, the needle will show 3/4 tank instead of full. Over the first 5-10 minutes of driving, though, it will even itself out and show approximately the correct amount of fuel.

The digital gauge (one that shows how many miles you have left to travel on your current tank) just doesn’t match the analog anymore. Used to be when I would fill up, it would say I had ~320 miles or so on the tank. Now after filling it up this morning, it seems to be stuck at 270.

The mechanic said it sounded like a sensor, expensive to fix, and I’m not too eager to dump a ton of money into this car. Any ideas as to what could be going wrong, and should the analog still last for awhile, even if it’s fluctuating? Any cheap(er) fixes?

It is most likely that your fuel level sender in the gas tank is failing. There is some cleaner that you can add to the gas that sometimes helps, but at ten years old…
Get ready to either replace the sender, replace the car, or live without an accurate indication of how much fuel you have in the tank.

If you want to see if adding a cleaner to the fuel system will help, try adding a product made by Chevron called Techron. It has fixed some issues like this for some folks.

The digital readout of miles to empty depends on the fuel guage for knowing how much fuel is in the tank. Since the fuel guage is off, that throws off the digital MTE also.

I suggest you use one of the trip meters on your odometer. Zero it out when you buy gas and fill up every set number of miles, like 300. The gas guage could get pricey to fix.