Actually, experts will tell you that you get your best gas mileage from the first half of the tank – for whatever reason, and I don’t know how or why.
But I think what this person meant is that if you fill it up when it’s only half empty, it just costs less money to fill it back up again, because you’re only filling a half a tank rather than a whole tank.
Okay, I’ll bite: how do you save money on gas by not letting your tank go below 1/2? I would think that keeping it below 1/2 would be better, because you’re carrying less weigh, and you can still improve your dollar average by stocking up when prices drop greatly. Very interested – I love to save on my car’s gas, LOL.