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Thread: Gas saving myths and truths

  1. #1
    Vulture of The Western World Eric's Avatar
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    Gas saving myths and truths

    Even though gas prices have settled down - for now - most of us no longer have the luxury of not worrying about how much we're spending on gas, even when it's "only" two-dollars-per. Here are a few things that can help - and which you may not have thought about before:

    * A car with a manual transmission always gets best gas mileage -

    This used to be true, in part because a four or five-speed manual transmission was more efficient than the non-overdrive, three-speed automatics that were common before the mid-1980s.

    But modern overdrive automatics have five, six even seven forward gears - as well as lock-up torque converters that virtually eliminate slippage between the engine and transmission when the car is cruising along. The "efficiency gap" has virtually closed - and a modern car with a modern overdrive automatic will typically get virtually the same gas mileage (plus or minus 1 MPG is typical) as the identical car with a manual transmission.

    In fact, it may do better in real-world driving (vs. the EPA's test loop) because an automatic is automatically always in the correct gear for any given situation - whereas with a manual, the driver is responsible for changing gears, as well as engaging and disengaging the clutch. If he's not shifting at just the right time, or riding the clutch/over-speeding (or lugging) the engine, fuel economy will suffer.

    * Buying a minivan or crossover instead of an SUV will save gas -

    Actually, not so much. Traditional minivans like the 2009 Kia Sedona and Chevy Uplander are rated by the EPA at 16 city, 23 highway. The Mazda CX-9 crossover wagon gets 16 city, 22 highway. This is pretty much par for the course for vehicles of this type. Meanwhile, a traditional large SUV like the Ford Explorer - with a much larger V-8 engine vs. the V-6s used in minivans and crossover wagons - is only slighter more consumptive, with an EPA rating of 15 city, 17 highway.

    Reason? Most minivans and equivalent-sized crossover wagons are nearly as heavy as similar SUVs - around 4,300 pounds is typical - so their smaller six-cylinder engines have to work harder to pull the load. The SUV's V-8, meanwhile, has power to spare and so can pull the weight with less energy expended - which means less fuel burned.

    Minivans and crossovers can save you money, however - because they tend to be considerably less expensive than similar-in-size/features SUVs. Especially traditional minivans, fully loaded examples of which can usually be bought for around $25k brand-new.

    * Cheap gas saves you money -

    Be careful. Sometimes, the least expensive fuel is fuel with the highest ethanol content. Ethanol may be "green" and "renewable" but it does not contain as much energy per volume as straight gasoline. That means your fuel economy will go down as the concentration of ethanol in your tank goes up. If you mileage drops by 5 percent, your "savings" at the pump of 5 cents per gallon may be a wash. Gas stations are supposed to post the ethanol content of their fuel at the pump; you can also sometimes find out which brands of gas have more (or less) ethanol than competitors by doing a little research on the Net - and shop accordingly.

    Another thing to know about ethanol: If you own a car built before model year 1990 or thereabouts, avoiding fuels with a high ethanol content is more than just penny-wise. These vehicles were designed to burn gas, not alcohol. You may experience drivability problems, in addition to loss of power and reduced fuel economy.

    And: Be extra careful using high-ethanol content fuels in cars from the '80s and earlier. The ethanol may cause dangerous deterioration of rubber fuel line hoses and gaskets not made to handle the much more corrosive alcohol content. This can cause seepage and leaks, which could lead to an engine fire. If you must use fuel with high ethanol levels because that's all that's available, regularly inspect the fuel lines and so on for signs of deterioration - and ideally, replace them as soon as feasible. Replacement hoses and gaskets will have been made to withstand modern fuels with high ethanol content.

    * Cutting the engine at traffic lights can save a lot of gas -

    Hybrids do this, so surely it's a way to reduce fuel consumption on other cars, too? Well, maybe - and maybe not. For one, it depends on the length of time you're stopped at a light or idling in traffic. It comes down to whether the fuel you save by not running the engine for "x" number of seconds (or minutes) is negated by the amount of fuel spent by restarting the engine.

    Two other factors to consider: If you're not driving a hybrid, you are really working your battery and starter by repeatedly stopping and restarting the engine. This could lead to early failure of either or both - and both are expensive to replace. Starters, especially. (And unless you're a pretty good home mechanic, you will likely have to pay a shop to install a new starter - plus the tow job to get the car to the shop). Hybrids have high-capacity battery packs and starters designed specifically for regular, repeated stop-start cycles, so they can handle the extra work. But your regular car may not.

    Lastly, stopping/starting your car - especially in heavy traffic - can be unsafe and/or annoying to your fellow motorists. Other drivers may not appreciate waiting as you go through the process of restarting the engine. And what if it doesn't start? Now you're blocking everyone else and have created a real problem.

    Bottom line, you probably ought to avoid shutting off your engine until you've arrived at your destination.

    * A clean car gets better gas mileage than a dirty one -

    This isn't just pyschological. It's aerodynamical (if that's a word!). A dirty car - especially if it's really dirty and caked with mud - creates more wind resistance and thus, drag - which hurts fuel efficiency. Mud and dirt also add weight - and the more a car weighs, the more gas it consumes. So you can indeed save money on fuel by keeping your car clean. It's also good for resale/trade-in value, because the paint will look nicer if it's regularly cleaned (and waxed).

  2. #2
    DonTom
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    "an automatic is automatically always in the correct gear for any given situation -"

    Not true when going down hill. Or do some automatics automatically downshift these days? It is sometimes even hard for me to keep up with the latest technology and I am not a bit technophobic.

    Otherwise, opposite is true. Only manuals are always in the correct gear for going down hill and it's done automatically as who even thinks about it?

    -Don- (Reno)

  3. #3
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by DonTom View Post
    "an automatic is automatically always in the correct gear for any given situation -"

    Not true when going down hill. Or do some automatics automatically downshift these days? It is sometimes even hard for me to keep up with the latest technology and I am not a bit technophobic.

    Otherwise, opposite is true. Only manuals are always in the correct gear for going down hill and it's done automatically as who even thinks about it?

    -Don- (Reno)
    Most new cars with automatics have "smart" automatics that adjust for coast/downhill and so on. They can even "learn" your driving style and adjust their operating characteristics accordingly!

  4. #4
    DonTom
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    Quote Originally Posted by Eric View Post
    Most new cars with automatics have "smart" automatics that adjust for coast/downhill and so on. "

    Do they even down shift to a lower gear so you don't have to brake as much? I mean without the use of the crusie control (cruise controls often do this).


    Quote Originally Posted by Eric View Post
    They can even "learn" your driving style and adjust their operating characteristics accordingly!

    Even my 1988 Chevy Biretta (2.8L V6, manual tranny) did that. And it was very noticeable after a battery change (or battery disconnected) as for the first five miles or so after, the engine would die at every stop and then be okay forever after.

    -Don- (Reno, NV)

  5. #5
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by DonTom View Post

    Do they even down shift to a lower gear so you don't have to brake as much? I mean without the use of the crusie control (cruise controls often do this).



    Even my 1988 Chevy Biretta (2.8L V6, manual tranny) did that. And it was very noticeable after a battery change (or battery disconnected) as for the first five miles or so after, the engine would die at every stop and then be okay forever after.

    -Don- (Reno, NV)
    Yep, they do!

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