Better MPG with premium spark plugs?

Discussion in 'General Motoring' started by gregl, Mar 2, 2006.

  1. gregl

    gregl Guest

    I have an '87 CRX Si that runs great and gets the expected mpg. Will I
    get better gas mileage with premium spark plugs and wires?


    gregl, Mar 2, 2006
  2. gregl

    jakedrob Guest

    I would say that decent plugs might do a little....probably better
    gettin new plugs/wires/rotor etc....BUT DONT spend your money on "split
    fire" type they are a scam and very expensive.
    jakedrob, Mar 2, 2006
  3. My '87 Integra ran best (typical commuter driving, not racing) with the
    standard NGKs. I tried Bosch Platinums and they performed worse. Never
    tried premium wires, replaced OEM with OEM. Routinely replaced
    cap/rotor every 30K, air filters at 20K. I used moderately sporty tires
    inflated to about 35 psi. My Integra delivered improved mpg with
    synthetic oil. I could get 36-38 mpg out of it on the highway moving
    right along with traffic (70+ mph) vs the EPA rating of 30 mpg.
    Overall, I got about 32 mpg. Probably the best compromise between
    utility/economy/fun-to-drive I've ever owned. [Crushed like a tin can
    when a Tarus wagon plowed into it's rear end so I'd have to say safety
    was also compromised.]

    dimndsonmywndshld, Mar 2, 2006
  4. gregl

    TeGGeR® Guest

    wrote in

    Unless your current setup is worn or defective and
    produces a poor spark, no.
    TeGGeR®, Mar 2, 2006
  5. gregl

    jim beam Guest

    it depends on what you mean by "premium". if it's something like ngk
    iridiums, and the rest of your ignition system is perfect and new, you
    can get maybe 1-2%. it's probably more important to ensure your
    distributor cap and leads are in good condition.
    jim beam, Mar 2, 2006
  6. gregl

    johngdole Guest

    From NGK Spark Plugs web site:

    Frequently Asked Questions

    Q: How much of a performance improvement can I expect from changing

    A: A common misconception is that changing spark plugs will result in a
    large power increase. In most cases, removing even seriously worn out
    spark plugs will only result in very modest power gains, typically
    about 1-2% of total engine output. This could be even less for
    computer-controlled vehicles, primarily because most newer vehicles
    have more powerful ignition systems and the vehicle's computer can make
    adjustments so that vehicle operation seems smoother and more seamless.

    Many people think that simply supplying more spark to the firing tip
    can and will combust more fuel. What they don't understand is that most
    newer cars' engines are so efficient that they are already burning all
    of the available fuel. Simply adding more spark voltage can't burn more
    fuel because there is no more fuel to burn.

    When a stock or near-stock engine is given a fresh set of spark plugs,
    peak efficiency is restored. The power gains that come from this
    restored state of tune are usually minimal. Any company that tells you
    that their spark plug will provide significant gains in power in a
    stock or near-stock engine is making blanket statements that may not be
    johngdole, Mar 3, 2006
  7. gregl

    jim beam Guest

    eh? you're very confused. mixture ratios vary, and spark energy
    requirements for complete combustion vary too, by over ten-fold. part
    of the ability of the plug to deliver those energy requirements are
    determined by things like electrode conductivity and morphology, i.e.
    design. hence, different plugs /can/ affect power output. sheesh, go
    to a library rather than regurgitate garbage off the net will you?
    jim beam, Mar 3, 2006
  8. gregl

    SoCalMike Guest

    not enough to make up the difference in price. the only "premium" wires
    are OEM, and plugs are whatever ND or NGK the sticker under the hood
    calls for.

    youll be better off making sure it stays in proper tune, change the oil
    every 5k, keep the tires inflated and the air filter clean.
    SoCalMike, Mar 3, 2006
  9. gregl

    SoCalMike Guest

    i definitely noticed a difference in the girlfriends RAV4 once it hit
    60k by replacing the OEM platinum plugs with new ones. the idle smoothed
    out noticeably.
    SoCalMike, Mar 3, 2006
  10. Maybe you should check the total resistance of a modern ignition system.
    Between the coil, distributor resistor, resistor wires, and plug
    resistor you can easily end up with over 50000 Ohms. How does a 0.001
    Ohm difference in the plug tip matter?

    It is true that the voltage needs vary vastly with compression and the
    electrode shape. I am unaware of any modern car that needs a pointed
    electrode to achieve a proper spark. They all have enough spare voltage
    and dv/dt to work with a plug that has been mildly worn to a dome.

    Also, modern low emission engines maintain the proper air/fuel ratio
    underneath the spark plug even when the rest of the chamber is lean.
    It's a valve and injector timing trick.
    Kevin McMurtrie, Mar 3, 2006
  11. My .02 is that it's WAY more important to gap the OEM replacement plugs
    to the correct gap than it is to buy some trendy exotic split-fingered
    merlotbrougham, Mar 3, 2006
  12. gregl

    johngdole Guest

    Yes, I've noticed the same thing with older plugs. When a difference
    like that is noticed, you know the factory specified interval has been
    stretched too long. I personally change plugs 30K miles.

    But replacing an old but properly working plug at the end of its
    service life may not give you more than 1-2% improvement with modern
    ignition system. Of course, how NGK arrivies at 1-2% is a different
    johngdole, Mar 4, 2006
  13. gregl

    johngdole Guest

    I agree with Kevin that a properly working iginition system is well
    capable of handling the voltage variations needed to spark the gap
    within the specified service interval of the plug. So changing out a
    good old plug at the end of its service life with a good new plug won't
    give you that much, as NGK stated, 1-2%.
    johngdole, Mar 4, 2006
  14. gregl

    Matt Ion Guest

    This is a very good point, however...
    Maybe I'm just being silly, but it seems to me that more voltage is
    simply better (within reason - if it's enough to breach the ceramic,
    that's a problem, but assuming that's not gonna happen...)

    You have two electrodes and an air gap. You need to generate enough
    voltage to cause a spark to jump that gap. The stronger the spark, the
    less likely it is that you'll get a misfire. The actual resistance may
    vary depending on the air/fuel mix floating through the gap at any given
    time, but in any event, you want a nice hot spark to ignite it: if the
    mix provides a higher resistance, you need more voltage to create the
    arc; if the resistance is lower, the arc may occur at a lower voltage
    and not be hot enough to ignite the mixture - either way, more voltage
    is better. I can't imagine any instance you'd actually want LESS
    voltage across the gap.
    True - the shape of the electrodes isn't as much a problem as having the
    electrode(s) wear down, thus increasing the gap excessively, or having
    deposits build up on them, thus decreasing the gap significantly, or
    adding "insulation" to them, thus reducing the spark efficiency.

    The spark plug is a pretty simple device, after all... its operation and
    design really hasn't changed that much in the last, oh, hundred years or
    Matt Ion, Mar 4, 2006
  15. gregl

    jim beam Guest

    ok, make that "thermal conductivity".
    it doesn't much when the plugs are new because the electrodes are nice &
    square, and those sharp angles have higher emissivity. but those sharp
    edges quickly erode, so skinny electrodes that can take the
    thermal/chemical environment make for better spark quality over time.
    add to that the fact that skinny electrodes have higher emissivity than
    fat ones day one, and retain it over time, and you /do/ have a better plug.
    red herring.
    jim beam, Mar 4, 2006
  16. gregl

    TE Cheah Guest

    | > >>From NGK Spark Plugs web site:
    I avoid NGK ; wears fstr than NipponDenso / Champion.

    | > > misconception is that changing spark plugs will result in a
    | > > large power increase.
    Bullshit ; changing from plugs with ( 4k ohm ) resistors to plugs w-o will
    get more amperes i.e. broader sparks, fstr burn, 5% more torque, 2% less
    noise, enable slower idling & a bigger gap for longer & even broader
    sparks ( another 1% more torque ).
    If replaced by plugs with electric wind design, then even fstr burn & more
    TE Cheah, Mar 5, 2006
  17. gregl

    markcharles Guest

    What plugs & wires do you recommend?
    markcharles, Mar 29, 2006
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