Originally Posted by 1999 White C5 Coupe
It is possible the system was designed that way.
I suspect the logic behind the software is that, at an estimated
45 miles to empty, the uncertainty of that number is such that you have 45 ± 35 miles to empty - ie, as low as 10 miles or less.
Perhaps such caution is carryover from the past, when these sort of measurements were more pie-in-the-sky than truly reliable numbers.
With today's injected motors, the computer can very accurately keep track of how much fuel has been burned since the last fill-up. But there is still some uncertainty of how much is left. Unless someone at the factory calibrated the level sensor during production, the computer cannot really determine when the pump is going to start sucking air - it's still guessing a little bit at how many miles are actually left.
So, in the interest of caution, at 45 miles left in the tank, the software is sort of going to panic mode and telling the driver "low fuel" meaning "get gas now, just in case".
I suppose, with modern manufacturing processes, the tank making process is more tightly controlled, and the the fuel level sensing function is better characterized, such that there is better estimation of how much gas is left in the tank.
But the old, experienced guys at the factory have told the software guys not to get too trusting of the readings