With gas prices shooting sky-high, some drivers are using every drop in their tanks before filling up, but running on empty to save a few bucks now can cost thousands more later.
Without enough gas in the tank, the fuel pump buried deep inside it can fail.
"If you run your fuel low, then the fuel drops down below the pickup on the bottom of the pump," said Bob Mullen, who owns the Lord of the Rings repair shop in Dallas, Texas.
With so little gas in the tank, even just turning a corner or parking on a hill can cause what's left inside to slosh from side to side.
That can expose the pump to air in the tank and even suck sediment and debris at the bottom into the fuel system.
"It can damage this pump, sometimes catastrophically," Mullen said. "To replace a pump like that on an average car would run anywhere from $500 to $1,500, sometimes more. You really do not want this thing to fail."
If the pump does fail, or you just run out of gas, there's even more to worry about.
"Not only does the engine die, but you lose your power steering and your power brakes, so if you're in heavy traffic or on the highway, this could be quite dangerous," Mullen said.
That alone is reason enough for some drivers to consider changing their ways.
"I'll keep that in mind, I guess, and fill up sooner than later," driver Juan Torres said.
AAA recommends keeping your gas tank at least a quarter full and making it a habit to put more in when it gets that low, even if you can't fill up all the way.