Four Gas Saving Myths

gas mythsIf you’re looking to save money on gas with the rising prices, you probably have already heard most of the steps you can take to save money on gas. There are, however, a number of myths where people think they are saving gas when they probably aren’t. Here are four of them presented by CBS News:

Keep The Air Conditioning Off: Many people believe that if you turn on the air conditioning in your car, you will be using more gas. But Consumer Reports and Edmunds did a study that indicated that using your air conditioner in most modern cars will not waste any noticeable amount of gas – so you don’t have to sweat through the summer heat in an attempt to save money.

Keep The Windows Rolled Up: Many people believe that keeping the windows rolled down will create drag and waste gas. Modern cars are quite aerodynamic and even when you drive with the windows down, it will have little effect on your gas mileage.

Restarting Engine Wastes Gas: This is a myth that has developed from a truth. When cars had carburetors, this was true, but most modern cars now have fuel injection systems which means if you leave your car running more than half a minute, it’s better to turn off the car than to leave it idling.

Wednesday Is The Cheapest Day To Buy Gas: While it is true that it is usually cheaper to purchase gas on a weekday rather than a weekend, which day of the week varies and there is no one particular day that is cheaper than the rest.

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6 Responses to Four Gas Saving Myths

  1. Captain America says:

    Just a couple of thoughts:

    I’m pretty sure #1 is wrong. When I run my AC I get 1-2 mpg less than if I run nothing at all. Now, my car only gets about 20mpg at best anyway, but you get the point. I know I’m only one “rather subjective” data point, but that’s all I’ve got.

    #2 also seems off. The more aerodynamic your car is, the more open windows will have an effect on your mpg.

    I guess in fairness, it does say “little effect”, and if little is somewhere

  2. mitchell says:

    #1 and #2 are conflicting. there was an episode of mythbusters on this.

    the idea is that if you’re not using AC, you have your windows down, which causes drag. they determined that all in all, windows down gives you an extra MPG or two over AC use.

    while the mythbusters tests aren’t always extremely scientifically sound tests, i have a feeling that windows down and AC on weren’t compared in the CR/edmunds tests, so neither set are ideal or thorough. so take both with a grain of salt, imo.

  3. ken says:

    if you are in slow moving traffic leaving your windows open can be an option.

    i find it a lot quieter when traveling at highway speeds with the windows closed and the ac on.

  4. Jason says:

    There is an article over at Omninerd where a person tested several different driving styles and how they effect fuel efficiency. It’s a good, though sometimes technical, read.

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  6. Useyourbrain says:

    Okay… instead of quoting conflicting “studies” which don’t reflect the true multitude of conditions in which you drive your car, how about we use a little noggin power?

    Your A/C compressor causes parasitic drag on your engine. It is turned (thus compressing freon and allowing cooling) via a belt that is attached to your crankshaft. How much effect this will have on your gas mileage will depend on how hard it is to turn your compressor, and how much power your engine is creating. I personally DO experience a decline in my gas mileage with my A/C on, but I have an old car with an old compressor and an engine that doesn’t have a lot of power to spare. If you drive a Diesel V8 truck with a small cab (and a small A/C compressor to match), you will probably not experience a difference. Wild claims meant to apply to all cars on the road under all conditions are silly. That being said, if you want to make a blanket statement, an accurate one would be that running your air conditioning will result in a net loss of power from your engine, which may or may not manifest itself in your gas mileage.

    The “windows down” debate is very similar. Aerodynamics barely even matter when you are traveling at slow speed because air is extremely fluid. However, the air applies 4 times more resistance for each doubling of your speed. So, when you are going 80 on the freeway, there’s a good chance that the utter destruction of your modern car’s very good aerodynamics will matter. However, at a constant speed, the parasitic drag of your A/C compressor isn’t likely to cause a lot of drag because your engine is not being used to accelerate the car (which requires a great deal more power than maintaining your current velocity).

    If you absolutely can’t handle using your brain to figure out how this applies to you, consider this rule of thumb: If you are going to be putting around town, it’s probably better to just have your windows down. If you’re on a cross-country road trip, turn on the AC… the 1 or 2 mpg you might lose isn’t likely to kill you.

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