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Thread: Truths and half-truths about fuel saving tips

  1. #1
    Vulture of The Western World Eric's Avatar
    Join Date
    Jul 2006
    The Land of The Edentulites

    Truths and half-truths about fuel saving tips

    Everyone's jumping on the "save gas" bandwagon - understandably. It's on everyone's mind. But that doesn't mean you ought to mind everything you read. While there's lots of good advice in circulation, some of it is outdated - or just flat out wrong.

    For instance:

    * Regular tune-ups will save you gas -

    Most new cars - indeed, most cars built during the past decade - do not need regular tune-ups of any sort. Spark plugs last as long as 100,000 miles; ignition systems are largely maintenance-free and the car's onboard computer makes regular adjustments automatically to assure peak performance - and economy. Unless the "check engine" light comes on, you should not worry about tune-ups until the time/mileage interval specified in your owner's manual.

    * Warm up your car before you drive off -

    In the days when cars were fed fuel by carburetors (and took several minutes to reach normal operating temperature) this was a good rule to follow. But cars haven't come with carbs since the late 1980s - and a modern car reaches normal operating temperature within moments of start-up. "Warming it up" only wastes fuel (as well as time). in fact, prolonged idling may be harmful to the vehicle as it actually delays full warm-up, which can increase wear and tear. The right thing to do is to start the car - and drive it.

    * Shut off your engine if you expect to be idling for more than 30 seconds or so -

    Hybrids save gas by shutting down the gas half of the gas-electric powertrains when the car comes to a stop. You can do the same thing without all the high-tech assistance of a computer - or the expense of buying a new Prius. Just turn the engine off when you hit a red light - or find yourself stuck in traffic. You can reduce your overall fuel consumption by as much as 5 percent this way. Just be aware that you may reduce the life of your starter motor - and you're working your car's battery harder than you otherwise would, which could and probably will mean it dies sooner than it otherwise would have.

    * Don't run your AC; roll down your windows instead -

    This is a "maybe yes, maybe no" fuel saving suggestion. Older vehicles - generally, those built prior to the mid-1980s - had AC systems that were very power hungry, with huge compressors that took a lot of energy to drive them. If you've driven such a car, you may recall actually feeling the load on the engine when the AC was turned on. If you have one of these old cars, you can indeed save some gas by limiting the use of your AC. But with modern cars, the potential fuel savings are lower because the AC systems in modern cars are much more efficient. They don't load the engine nearly as much - and you might actually end up burning more fuel by rolling down the windows and increasing the car's aerodynamic drag. Rule of thumb: If your car is a 1990 model or newer, running the AC probably won't increase your fuel consumption much - if it's even noticeable at all.

    * Keep your car washed and waxed -

    Some people believe a clean car drives better than a dirty one - and they may be on to something. A smooth, clean surface cuts through the wind more efficiently than a bumpy lumpy one. Increased wind resistance means higher fuel bills - though the increase is probably very small, for the most part. With one exception: If you have a truck or SUV and have taken it off-roading, caked-on mud clinging to the undercarriage and fenderwells can add a surprising amount of weight to the vehicle - as well as increase drag. A session with a power washer can get your fuel bills back to where they ought to be.

    * Using lower-cost "regular" gas to save money -

    This is fine, if your vehicle was designed to burn regular unleaded. If, however, you happen to own a vehicle designed to run on high-octane premium fuel, filling up with regular is a bad idea because your engine's efficiency will be reduced - and you'll probably end up getting worse gas mileage, as well as reduced performance. To maximize the fuel economy potential of any engine, it is important to use the type of fuel it was designed to burn - whether that fuel is 87 octane regular or 93 octane premium. It's just as counterproductive, incidentally, to burn premium gas in an engine built to run on regular. You won't get more performance - and you may see a mileage loss - as well as the loss you'll pay up front for buying the higher-cost premium fuel.

  2. #2
    Senior Member misterdecibel's Avatar
    Join Date
    Apr 2007
    Little Rock, Arkansas

    Re: Truths and half-truths about fuel saving tips

    My car's air conditioner takes a rather large toll on in-town driving, but makes minimal difference at constant highway speeds.

  3. #3
    Senior Member
    Join Date
    Feb 2007

    Re: Truths and half-truths about fuel saving tips

    Posted this article on the main site:

  4. #4
    Join Date
    Aug 2006
    Houston, TX

    Re: Truths and half-truths about fuel saving tips

    Nice article -

    Regular Tune Up
    I check my spark plugs every 50,000 miles or so. It seems as if they tend to wear out after that period of time. The 100,000 mile tune up is a farce. Tuning up doesn't affect gas mileage, however.

    Shut off engine

    I have found that it works. I shut it off at longer stoplights and it is true that it results in shorter starter life, although mine lasted around 140,000 miles. The $200 cost of the starter was already saved in reduced fuel bills.

    A/C versus windows

    AC definitely burns more gas than rolling down windows even in a modern car. A friend of mine tested this and found a 2-3 mpg drop in gas mileage at all speeds between 55 and 75 mph in his Kia Sportage.

    Premium versus Regular

    All things being equal, I believe that a car designed to run on Premium will get better efficiency than one designed to run on regular. On the other hand, no one really knows how much of a difference that would make. I run Plus in my car, which is known to lower combustion temps somewhat. Since the difference is only 10 cents per gallon out of a 4 dollar price, my view is "who cares?"

  5. #5
    Senior Member J. ZIMM's Avatar
    Join Date
    Mar 2008

    Re: Truths and half-truths about fuel saving tips

    Changing spark plugs? My Great Monkey has a 104k on the clock, still gets 27 mpg's and ,,,YOU MEAN THIS THING HAS SPARK PLUGS??????? ???

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