The lowest I've seen to date was 48 miles remaining when the fuel light came on. I drove two miles at 55mph from the dealer to the nearest gas station, and put in 24.85 gallons. I've put in as much as 25.1 previously. Since my fuel economy says 12.9mpg (horrible), if there were two gallons remaining it should have read '25 miles remaining', but said 48 when the light came on (this V8 couldn't get 24mpg if it was on a tow truck.
Still, If you consider that I only drove a couple miles at 55mph, there should have been roughly 2 gallons left in the tank at the point I put 25 gallons in it, meaning I have A 27 gallon fuel capacity. Which seems impossible, even if the expansion reservoir accounts for a couple of extra gallons (which will fill if you pump slowly).
What this tells me is my 'low fuel' light comes on when there is less than a gallon left, which is dangerous in rural Wyoming, especially in winter when it can be -20F at times (-15F so far this year). I don't generally run my car that low, but my wife does it all the time.
Worse, when I filled it with just over a half tank showing (post above), it took on 17.1 gallons, which means it is simply not reading properly. Given the long distances between gas stations, mountain passes and cold temps where I live, it's really bad having a substantial overestimate of how much fuel you have on board, especially at a half tank or less. Basically, a half tank is more like 1/4 tank, and 1/4 tank might only be a few gallons remaining.
It should go without saying that engineering an accurate fuel gauge should be an achievable feat of engineering in 2022... yeesh.