The fuel gauge on my '99 Cutlass has been acting strange for a few years. It works fine from full until just under 1/4 tank and then works its way back up until it registers full. When it gets back to full, I know it’s time to refill. I use the tripometer to keep track of whether the tank is in the first 3/4s or the last 1/4. It’s not a big problem for me but can cause huge problems when someone else drives and doesn’t realize the gauge is working backwards and the tank is nearly empty.