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Thread: Best Spark Plugs for Fuel Economy?

  1. #21
    Senior Member Mitz's Avatar
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    I have the Denso (4703) IKH16TT Iridium TT Spark Plug as spare. I'd probably sell it and buy the Ruthenium to keep as spare instead.



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    Quote Originally Posted by Tyrelirwin View Post
    This makes sense to a point, but doesn't consider the economics of car design, or the advancement of technology in the interim. Maybe mitsu just has a good bulk-deal contract with NGK?
    Denso or NGK Iridium plugs gapped @ .044 are excellent spark plugs. Mitsubishi is not putting a cheap plug in the Mirage. Iridium is 25% harder than platinum.

    I've heard of people going 200,000 miles on Iridium plugs without issue. If you are only changing your spark plugs every 100,000 miles without issue, spending approximately $9/iridium plug seems well worth it to me.

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    Quote Originally Posted by Mark View Post
    Denso or NGK Iridium plugs gapped @ .044 are excellent spark plugs. Mitsubishi is not putting a cheap plug in the Mirage. Iridium is 25% harder than platinum.

    I've heard of people going 200,000 miles on Iridium plugs without issue. If you are only changing your spark plugs every 100,000 miles without issue, spending approximately $9/iridium plug seems well worth it to me.

    Gotcha- you're saying "go with the stock suggestion" not becuase it's "stock", but because of the plug's individual merits.

    I am personally always willing to assume that technology advances and something better will come along. That plug design is what, 5-10 years old? Tech moves fast.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 automatic: 36.9 mpg (US) ... 15.7 km/L ... 6.4 L/100 km ... 44.3 mpg (Imp)


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    Quote Originally Posted by Tyrelirwin View Post
    Gotcha- you're saying "go with the stock suggestion" not becuase it's "stock", but because of the plug's individual merits.

    I am personally always willing to assume that technology advances and something better will come along. That plug design is what, 5-10 years old? Tech moves fast.
    There are trade offs with different types of plugs. Thus, it may be best to just go with what the manufacturer suggests in the first place. If I drove V6 engine that had plugs that were difficult to reach, iridium is the way to go.

    There are two quotes below - one sells you on iridium, & the second makes you take a pause. A newer style Ruthenium plug is also on the market.

    "Iridium is said to be six times harder and eight times stronger than platinum with a 700° higher melting point. Iridium spark plugs have extremely fine electrodes while retaining excellent wear characteristics. Thanks to its strength, iridium spark plugs can last up to 25% longer than comparable platinum spark plugs."

    "Platinum and Iridium plugs perform at a lower level than copper spark plugs, because they are less conductive and they tend to overheat. ... However, the overall longevity of these two types of metal is better than copper plugs. In reality, copper has the best performance of all three and the worst longevity."


    It's hard to get a straight answer on things like this. I do think NGK & Denso iridium plugs are quality plugs. I would not second guess using either one.

  5. #25
    Moderator Eggman's Avatar
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    Quote Originally Posted by Mark View Post
    "Platinum and Iridium plugs perform at a lower level than copper spark plugs, because they are less conductive and they tend to overheat.
    Not that I'm any authority here but I'd have to think that the difference in resistance is marginal at best, especially at the voltages used for ICE spark.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Quote Originally Posted by Eggman View Post
    Not that I'm any authority here but I'd have to think that the difference in resistance is marginal at best, especially at the voltages used for ICE spark.
    You will find information indicating race cars & high performance engines will use "old fashion" good quality copper plugs. Thus, there may be some merit to this claim.

    The Mirage is not a race car, nor a high performance engine. In all honesty, I haven't changed plugs. I am just over 20,000 miles on my 2017 Mirage. When it comes time to change them, I am going to replace them with stock plugs (or whatever I can find closest to that). Changing plugs every 100,000 miles is such a small maintenance item in my mind. I don't miss the days of ignition points, condensers, distributor caps, & carburetors!

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    Moderator Eggman's Avatar
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    I recall some old timey spark plugs came with resistors...

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    For japanese cars or any car really I tend to use NGK I also like ac delco for domestics and bosch for european but ngk is best

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    Quote Originally Posted by Mark View Post
    I think to much has been made of spark plug choices. Using/changing recommended NGK or Denso Iridium spark plugs every 100,000 miles is not a big deal.
    agreed I guess I have cared because I have driven so many cars where it needed done nice thing about this car is I have 100k before I need to care

  10. #30
    Senior Member MacClyver's Avatar
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    I was looking into this a few years back.
    https://geometroforum.com/most-effic...ug-t52154.html
    From what I can tell reading all spark plugs are copper and then plated with Nickel, Platinum, or Iridium. Seeing as higher electrical resistance would mean more energy is lost as heat, in theory the spark plug with highest conductivity would be most efficient.

    Values found here.

    σ(S/m) at 20°C
    Nickel: 1.46x107
    Platinum: 9.44x106
    Iridium: 1.891x107

    Iridium has the highest conductivity of the three, so it would lose the least energy to heat as electricity passes through it. And it's possible that at ≈1000°C that Iridium is not the most conductive but conductivity tends to be fairly linear.

    Of course there are many other factors at play also.
    Going off my theoretical assumptions I got the Denso Iridium TT, as the Rhodium/Iridium alloy and pointier electrodes would point to less energy needed to produce spark.

    I only drove with them for a few months before switching cars so I wouldn't be too conclusive, but the science made sense.




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