Old habits die hard. Old folklore dies even harder, and it may be costing you money by burning excess fuel. From letting the car warm up before you drive, to starting and stopping the motor, we’ve dug into the car myths that are causing you to lose the most money.

The myths:

  1. Letting the engine come up to temperature. People will often say you can’t drive until the motor is up to operating temps. While this may have been good advice 30 to 40 years ago, it isn’t true anymore. Modern engines have an onboard computer, the Engine Management System (EMS), to moderate them. The EMS won’t let the engine perform in a manner that could damage the engine. Should you hammer the gas and get up to 80 right off the hop? No, but the drive to the freeway should be long enough to get it up and going without too much stress. Save fuel by driving conservatively with a cold engine—no need to waste fuel and pollute the air by idling.
  2. Rolling the windows down is better than running the air conditioner. Again, modern vehicles are well managed by their onboard computers. Also, it doesn’t cost you much extra fuel to run a modern AC system. But rolling the windows down, especially at speed, can affect the car’s aerodynamics, reducing your fuel economy.
  3. Buying gas early in the morning, or when it’s cold outside, gives you more bang for your buck. Simply put, science isn’t behind this. A sealed container of gasoline at 45° F still has the same number of molecules as when the container is at 80° F. Since modern engines account for fuel in the cylinder almost down to the atom, a minor change in volume won’t do much. Not to mention, gas stations store fuel in underground containers where the temperature doesn’t change a whole lot.
  4. Running the heater saves or uses more gas. Both are untrue, with the exception of old Volkswagons with gas heaters. The cabin heater in your car is a smaller version of the radiator that blows air into the car. Coolant flows through the engine, then passes through the heater core. Air blows through, pulling off heat and keeping your toes warm. Except for the fan, it is a passive system. Some people argue that running the heat saves gas because it increases the cooling surface. If you’re looking to save fuel in the winter, it’s more related to slower driving or fewer miles. If you see a decrease in mileage, it may be a result of the winter gas used in colder climates.
  5. Starting and stopping the engine uses a lot of fuel. This is one of those holdovers that might have been true years ago but isn’t anymore. Again, the EMS is running the show, and it’s aware of what’s going on. Old, carbureted cars sputtered and chugged to life, the mechanical fuel system pushing gas everywhere. Fuel-injected vehicles don’t use fuel until the starter motor gets the engine spinning.

If you want to save fuel while driving, there are a few things you can do to see real improvement in your mileage. Drive with more caution, avoiding sudden starts and stops. Keep your car well maintained—not just the engine, but the body too. Aerodynamics can get thrown off by the smallest dents or missing trim pieces. Keep your tires properly inflated. And avoid hauling around weight that you don’t need.

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