There’s a fierce debate between car owners regarding filling their fuel tanks. Is it most appropriate to wait until it’s near empty, or fill it up when it gets to a half tank?
People who fill up when their tank is half empty believe it’s not a good idea to let the tank run near empty. This is because if there is any moisture, or any contaminants, in your fuel, you risk sucking those dregs into your engine, potentially causing damage to the engine.

The opposing theory is that less weight means you get a better fuel economy, so running the car with as little fuel as possible makes that fuel go a long way.
Although it’s true that there is still enough fuel left in the tank when the gauge is on “E” to get to a gas station, it’s safer not to count on having any reserve fuel, and rather just filling up when your fuel is running low.

A good compromise amount is refilling when the tank gets down to a quarter tank. This eliminates any risk associated with your tank being too empty to function, and also allows you to run on as little fuel as possible while still maintaining enough to fuel to get you to a petrol station.

As a general tip, if you’re not driving your car for an extended period of time, it’s best to leave the tank full for this period, as this reduces the likelihood of the fuel going stale through exposure to air in the tank, or contamination.