Why do we get better gas mileage in the summer months?

  • Why do we get better gas mileage in the summer months?

    Here’s something many people may not know: fuel efficiency improves during the summer months. NACS provides an excellent explanation here, with four key reasons displayed below:

    A number of factors, all weather related, can increase fuel efficiency by as much as 10% during the summer months, regardless of the type of fuel purchased:

    1. Engines are more efficient: In the colder months, it can take longer to start a car and multiple cranks of the engine waste fuel. In addition, many drivers give their cars a chance warm up, whether to defrost windows or heat the interior. This idling detracts from fuel efficiency. But even without this idling, car engines are less efficient when cold. It may take a while for a cold engine to achieve peak efficiency and on extremely cold days it may never achieve peak efficiency. Overall, engines perform much better when outside temperatures are 90 degrees, not 20 degrees.
    2. Ice and snow detract from mileage: Ice and snow can hurt mileage, whether on the roads or on a vehicle. Cars are likely to spin their wheels under icy conditions, reducing mileage. Also, drivers tend to travel at less fuel-efficient speeds under poor road conditions brought on by extreme winter weather. In addition, any snow or ice on a vehicle adds weight and makes the vehicle less aerodynamic — as does any weather-related grime on the vehicle. One more thing: Hot air is less dense than cold air. All things being equal, a vehicle is more aerodynamic travelling through hot air.
    3. Better tire pressure: Tires lose air pressure in colder temperatures. If a tire’s air pressure isn’t adjusted in the colder months, it will be flatter and increase resistance and friction, leading to reduced fuel efficiency. The opposite occurs in the warmer months, and fuel efficiency can increase.
    4. Lubricants perform better: A car’s oil is more viscous (thinner) when it is warm and engines perform more efficiently when oil is thinner. The same holds true for all other lubricants. In addition, people take better care of their vehicles when it is warmer outside. They are more likely to change the oil and conduct other routine maintenance that can improve fuel efficiency.

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