Spark plugs are the single most important part of your tune up.

The leading questions over the past few days ask about tune-ups. Whether it’s for an older or newer car the task is the same, getting the gasoline fuel’s energy into moving the car efficiently. Most of us know that the tune up is mostly about spark plugs and the reason is that the common estimate has it that a bad spark plug can take down your efficiency by 30%. At that rate it won’t take long to buy those plugs.

Of course it’s not so simple as that, or the questions wouldn’t have come. The main question is which spark plug to choose?

The purpose is to light off the compressed air and gasoline mixture in the cylinder, on time, every time. There are lots of pages on the web to explain that, but for our purposes, the goals are the same as a racer, a hypermiler, or a lawn-mowing contractor. That means no misfires or as few as possible. Because misfires allow that cylinders air fuel mix to escape unused, the engine, by using the throttle or the computer will compensate with even more air and fuel to meet the expectation to go. Worse yet is the unburned air fuel mixture is shortening the life of your O2 sensor and catalytic converter, both of which are expensive items to replace. That makes two real important reasons, saving fuel money and saving extra maintenance expenses for keeping up the spark plug’s replacement schedule.

Years ago I read an article that I recall was written by maybe Barry Winfield or Patrick Bedard in Car and Driver Magazine. When I checked the Car and Driver Site the search archive only went back to year 2000 so my recollection must suffice until one of the guys responds to the email I sent today. I’m using the Denso Iridium spark plugs that I recall the article as listing from a test as having the fewest misfires.

The job of the spark is simply to provide ignition to the air fuel mix. There are “pulse plugs” and other designs that are available. But the available watts in the spark are determined by the coil voltage and amperage, which isn’t going to change no matter what the plug maker claims. Spark plugs operate in a wide range of conditions, maybe from minus 40F for a northern area cold start to hundreds of degrees or over one thousand degrees in a maxed out turbocharged engine under load. So the engineering is pretty sophisticated.

A good guide until I get a third party test result would be what manufacturers use in new cars. All the carmakers are assiduously designing, engineering, and testing configurations to maximize the power and fuel efficiency of their products. That’s balanced against what spark plugs cost so a low priced car will be sold with something that costs less in the trade off for getting the price of the car down. On the other hand the high-end car will get the top choice perhaps without any regard to the cost. It’s pretty common to see platinum plugs installed across a wide range of cars from many makes. At the high end you will see the iridium plugs installed.

So there you go. But all of this is worthless if the spark plug wires from the distributor are in poor condition. A coil’s electrical pulse that’s stopped or bleeds off by a spark wire that’s shorted or running a high electrical resistance won’t fire the plug. It’s another way to get a misfire.

And lastly check the distributor cap and rotor. A fouled cap full of little black carbon tracks either inside or outside allows that pulse to go to ground somewhere other than the plug. Look at the terminals of the rotor and inside the cap, too. The coil pulse will come in from the center of the cap, jump across to the center of the rotor, travel out to the rotor end and jump through the air over to the cap terminal before it goes down the spark plug wire. It’s a busy place where lots of problems can be found.

If the terminals of the rotor and cap are complete meaning not eroded away and there is simply dirt, grime and some burned carbon on the terminals, just prick the burned carbon off of the terminals with a fine sharp instrument and give the rotor and cap a scrubbing with soapy hot water and blow dry. You will truly notice the difference.


29 Comments so far

  1. Henryk on April 11, 2008 3:11 PM

    Best are The Revolutionary FireStorm Spark Plug.

    Fire Storm Capabilities
    First, let look at what Krupa FireStorm spark plugs give an
    combustion engine:
    More horsepower;
    44-50% increase in mpg;
    Dramatic decrease in emissions.
    Second, let see what FireStorm plugs eliminate:
    Smog pump;
    Catalytic converter;
    Radio frequency interference (RFI) and the use of resistors in the
    Gap growth;
    Exhaust gas recirculation (EGR) systems;
    Misfire/hesitation/detonation/stutter and stumble

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  4. Anonymous on July 1, 2008 12:41 PM

    I just bought a brand new vehicle on June 30th, 2008. I bought the firestorm plugs and saw no improvement in gas mileage. If it did imptove it, it was such a small amount you cannot even tell. Disappointed customer…does not suggest these. I would bet the EPA would agree with this comment asw ell.

  5. Henryk on July 6, 2008 5:59 AM

    What for of the stupidity , with bought FireStorm Spark Plug he produced is not

  6. Anonymous on July 6, 2008 8:06 PM

    he cant buy something not available to the market,must be ac delco

  7. OZZMAN on October 2, 2008 12:20 PM

    What i like to know is where did this anonymous person buy plugs, that are not in production?

  8. Mark Foster on December 8, 2008 11:58 PM

    When will the firestorm spark plugs be available?

  9. Henryk on January 20, 2009 3:40 PM


    FireStorm Spark Plug probably in 2009r

  10. Triz on February 20, 2009 9:56 PM

    Thank you so much!!! I love all your blogs!


  11. John on May 11, 2010 5:57 AM

    A spark plug will never increase gas mileage by 50%


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  15. Mike Freimuth on October 14, 2010 12:42 PM

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  24. Ola on April 5, 2011 7:26 AM

    Superb post. However, I want to know if you could write a little more on this subject? I’d be very thankful if you could elaborate a little bit further. Cheers!

  25. Want The Best on August 15, 2011 11:30 AM

    Growing up, the main focus when it came to car maintenance was the sacred “oil change”. No one ever even talked about spark plugs! My car has almost 150,000 miles on it- I’m off the check those buggers out right now! Thanks for the great info!

  26. Chet Pistilli on August 29, 2011 9:12 PM

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  28. Braus on October 10, 2011 5:18 PM

    Can someone please tell me why they put resistors in the central electrodes of almost all automotive spark plugs? Please don’t tell me it’s to stop radio interference. If that’s the case, why don’t they put them in aircraft and marine plugs? Robert Krupa correctly stated that conventional spark plugs fire 6-8 times then misfire once, resulting in unburnt fuel passing out the exhaust system and costing you money. This is a well known fact in the automotive world. It’s called built in inefficiency. Even innovative multiple ground plugs like Brisk LGS and Zex plugs, which incidentally work far better than standard plugs, still have resistors in the central electrode. Why? The plugs are deeply set in modern engines usually with coilovers and are well shielded. Resistors are unnecessary. All they do is make engines less efficient and waste fuel which seems to be what the manufacturers want. Someone should start making non resistive Firestorm spark plugs available NOW. If you are like 99% of the population, you have been well and truly sucked in, the plugs in your car were designed over 100 years ago and are costing you money as they are wasting an enormous ammount of fuel. God save us from idiots and ourselves.

  29. Braus on October 10, 2011 5:30 PM

    Many plug manufacturers are now making multiple ground plugs which is great – but they all still seem to be resistive. Why? Are they bound by an industry standard to reduce efficiency??
    Can anyone please show me a multiple ground plug which is non-resistive? Thank you : )

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