Menu Home Blog About Us Work we do Content Contact Us Advertisement There’s an internet meme that surfaces every now and then: “It’s better to fill your car with gas in the morning, when the temperature is cold, rather than the afternoon, when it is warm. You get more gas that way.” Image: Henri Bergius Really? Is that true? Do you really get more gas when it is cold? Because gasoline is a fluid, it is denser when it is cold*. Since we purchase gasoline by volume, there is real science behind this; there will be a difference in volume at different temperatures (after all, this is how hot air balloons work! Heat up air, and it becomes less dense than the surrounding colder air. If you trap this hotter air inside an envelope, through the principle of buoyancy , you can generate lift). *Just about all fluids get denser when they get colder. ...