Two-piece spark plugs

Discussion in '2005+ Mustang GT 4.6L Tech' started by RetDrumSgt, May 20, 2022.

  1. RetDrumSgt

    RetDrumSgt Member

    I've read a number of post on this site regarding the difficulty of getting the two part, spark plug out of the block. In addition to following this site I've done a fair amount of research on the 2008 Mustang GT/CS convertible and came across an article about the plug and how to tell if your car has them.

    Today I had the car serviced and talked with my mechanic about the two part plug. He suggested if the car had the two part plug he recommended a tune up and pug replacement between 60 and 70,000 miles. If the car had the one piece plug he was OK, with the 100,000 mile as outlined in the manual. Him citing the difficulty with the plugs separation.

    Again, referring to the article on the plugs it stated if the car was manufactured pre November 2007 it will have a black coil boot and two piece spark plug. If the car was manufactured after that date it will have the revised 12mm one piece plug with a brown coil boot.

    When they pulled the plug I was pleased to see the brown boot.

    Mustang cut out.png
  2. 86GT351

    86GT351 forum member

    There are mileages that they state. We always suggest to replace them before that time. The more mileage, the more the plug gap increases and that can cause the vehicle to not run as efficient as possible.
  3. 07 Boss

    07 Boss Senior Member

    I'm an old fart so I pull my plugs a couple times a year to inspect and clean them. We seem to rely on sensors and computers and this is one of the old school ways of seeing the health of your engine. The added benefit is that if run the two piece plugs it will prevent them from building up all of that carbon and getting stuck. I know it is completely unnecessary but old habits....

    I don't run the two piece plugs anymore but when I did I never had an issue with them getting stuck. Currently running a combination of Brisk Racing and Accel one piece plugs.
    JeremyH and bambam 06 like this.
  4. skwerl

    skwerl tree hugger

    Be aware if you run the newer high end Iridium plugs that they all look the same. The plugs in my F350 looked perfect but I changed them and my mileage went from 5.86mpg to 6.8mpg (pulling a 7000 lb trailer).
    dark steed likes this.
  5. RetDrumSgt

    RetDrumSgt Member

    That brings up the question which plugs does the group recommend for my 2008 Mustang GT/CS. Used for street use only, no track.
  6. GlassTop09

    GlassTop09 Member

    For what you've typed RetDrumSgt as your usage of your car, the MotorCraft HJSF-24FP (official Ford OEM replacement) Double Platnium 12mm spark plugs should do you just fine.

    Now, if you desire an iridium cross matched plug (same heat range as the OEM plug thus an OEM replacement but iridium tipped so they last longer......only difference between the 2), I'd recommend the NGK Iridium IX ZNAR6AIX-11 (0372) 12mm series plugs as IMHO these are the best of the best for a stock\lightly modified 4.6L w\ 12mm heads but make sure that they are the 0372 series (.044" std gap) & not the 7554 series (.031" std gap...for FI engines). They do cost more than most of the rest of the offerings out there so be aware of that.

    You can't go wrong IMHO w\ either choice for your steed.

    Hope this helps.
  7. RetDrumSgt

    RetDrumSgt Member

    Thanks for the input.
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