Turns out a bunch of the stuff we’ve heard isn’t true anymore!

A dirty air filter drops gas mileage

Tests show that driving with a dirty air filter no longer has an impact on fuel economy, as it did with older engines. That's because modern engines use computers to precisely control the air/fuel ratio, depending on the amount of air coming in through the filter.

Filling up when the air is cool gets you more gas
A common tip is to buy gasoline in the morning, when the air is cool, rather than in the heat of the day. The theory is that the cooler gasoline will be denser, so you will get more for your money. But most stations store the gasoline underground, so its temperature changes very little, if at all, during a 24-hour stretch. Any extra gas you get will be negligible.

Driving with windows open hurts fuel economy
Some people advise you not to run the air conditioner because it puts more of a load on the engine, which can decrease fuel economy. But others say that opening the windows at highway speeds can affect gas mileage even more by disrupting the vehicle's aerodynamics. In tests of a Honda Accord, using air conditioning while driving at 65 mph reduced the vehicle's gas mileage by more than 3 mpg. The effect of opening the windows at 65 mph was not measurable.

Learn what other tricks are myths here.