In previous columns, we've discussed the importance of always filling all the way up when going to the gas station. The reason? The fewer trips you make, the more fuel you save, plain and simple. But you also do not want your gas tank to get to the brink of absolute emptiness, either. According to the insurance company Esurance, you "risk burning out your fuel pump and collecting sediment in your gas tank." Over time, the sludge clogs the fuel injector and can damage the engine. It recommends filling up on gas when you're "not running on fumes." I recommend any time you fall beneath a quarter of a tank of gas.