If you've ever found yourself waiting to fill up your car until after the sun goes down, you're not alone. But is it true that you lose gas in the heat of the day? KVUE set out to verify.

First, we spoke to an automobile expert. General Manager of Advance Auto in North Austin, Bob Flowers, tells KVUE that there is some truth to the fact that you lose gas if you pump during the hottest part of the day.

"I've heard it and it makes some sense,” said Flowers. However, he says the amount of gas is so minuscule it doesn’t make a difference.

Gas expands in heat, about 1 percent for every 15-degree change in the fuel's temperature. However, the gas that’s pumped into your car comes from an underground tank which is cooled.

KVUE also spoke to Petroleum Engineer Todd Brooker from Cawley Gillespie & Associates in Austin. Brooker agrees there is no “optimal” time of day to fill your tank as far as cost goes since the amount of fumes released is so minimal.

However, Brooker does say that it’s better to fill up in the evenings from an environmental aspect.

In addition, Flowers says it’s important to fill up before your tank gets too low to avoid damaging your fuel pump.

"If you let your tank get really low, and then you fill it up with cold gas after you've been driving for a long time, a lot of times that'll shock the fuel pump. Probably about nine times out of ten that we have to replace a fuel pump, the tank is full and they just got gas."