Keep your gas tank over ¼ full if possible. This will reduce condensation in the tank, which mixes water with fuel. Obviously, water in the gas is never good for your engine.
First, the fuel gauge isn’t always accurate. In fact, how precise your car’s gauge is relies on a variety of factors, including your driving style and your car’s fuel economy. According to experts, you should consider it more as an estimate — rather than an exact measurement — of how far you’ll make it before running out of gas.
According to Consumer Reports, the gas in your car “acts like a coolant for the electric fuel-pump motor, so when you run very low, this allows the pump to suck in air, which creates heat and can cause the fuel pump to wear prematurely and potentially fail.”
And the repair could cost a couple hundred dollars — more than what it would have cost you to fill up the tank. Also, “if there is dirt in the fuel tank, it could lead to blocking the fuel filter” — leading to another expensive repair.
Thanks to Clark Howard for some of these suggestions.