AF: Frequency of changing spark plugs | Allpar Forums
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Frequency of changing spark plugs

Discussion in 'Repairs, Maintenance, Help' started by AllanC, Aug 4, 2020.

  1. AllanC

    AllanC Well-Known Member

    Joined:
    Jan 6, 2003
    Messages:
    4,531
    Likes:
    1,122
    I just recently inspected the spark plugs in my 2016 Jeep Patriot with 2.4 liter 4 cylinder engine. All 4 plugs had a brown, tan tint and looked good with no signs of plug fouling. Even the center electrode had very little wear and was not rounded. I cleaned the plug tips with sandpaper, set proper gap and reinstalled with anti-seize compound on the threads. I did this more as a curiosity satisfaction and not because there was an engine performance issue or diagnostic code set.The engine has crossed the 60,000 mile mark.

    The owner's manual recommends replacement at 30,000 mile intervals. And Chrysler tends to follow the 30,000 mile replacement interval for spark plugs on many of its engines. In this particular instance I see no reason to replace the spark plugs and plan on continuing to use them to at least the 100,000 mile mark. Why does the manufacturer seem to set a rather arbitrary and low mileage interval for spark plug replacement?
     
  2. DC-93

    DC-93 Well-Known Member

    Joined:
    May 1, 2014
    Messages:
    3,170
    Likes:
    2,067
    For better performance, fuel economy and lower emissions.
     
    Bob Lincoln likes this.
  3. Doug D

    Doug D Virginia Gentleman

    Joined:
    Aug 10, 2000
    Messages:
    14,534
    Likes:
    4,009
    The owner's manual for my '06 Dodge Ram 1500 w/Hemi indicates 30,000 mile intervals as well. Except for the first change at 35K miles I have done them at 100K mile intervals. The plugs do show some moderate wear, but otherwise look fine. At best the fuel mileage after changing showed a 0.5 mpg gain. No noticeable power gain either. Truck now has over 270K miles on it. Changing the 16 plugs on a Hemi is not an enjoyable experience. On average it take 3.5-4 hours to change them out. The dealer charges over $300 for the service.
     
  4. ImperialCrown

    ImperialCrown Moderator
    Level III Supporter

    Joined:
    Jun 8, 2008
    Messages:
    21,189
    Likes:
    4,388
    The Copper-Nickel spark plugs still have a 30K mile service interval. The Platinum, Iridium or Ruthenium plugs have a 100K mile service interval.
    The 2.4L is available in 2 different versions; the conventional emissions with 30K plugs and the PZEV with 100K plugs, so it depends on which one you have.
    For best results, always use the OEM plug specified for your application.
     
    AllanC, Bob Lincoln and DC-93 like this.
  5. valiant67

    valiant67 ...

    Joined:
    Jan 7, 2003
    Messages:
    36,664
    Likes:
    19,406
    I've had two Hemi powered cars (2005 300C and 2007 Dodge Magnum) that I bought used. Both had the original plugs when I changed them (90k for the Chrysler, 130k for the Magnum). I did notice beter performance on the Magnum and a smoother idle. Not bad for cheap 30k mile plugs.

    Later Hemis switched to a longer life plug.
     
  6. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    31,880
    Likes:
    5,195
    The previous owner of my non-PZEV car let the original plugs go to 95K miles, instead of changing them at 32K. By the time I got the car, it ran great around town, but on moderate grades at highway speed, it was skipping and bucking. I pulled the plugs at 99K and found they were badly eroded, probably a 0.100 inch gap. It's amazing that they still fired. I change them at 32K.
     
    AllanC and ImperialCrown like this.
  7. 1999 White C5 Coupe

    Level 2 Supporter

    Joined:
    Jul 11, 2006
    Messages:
    498
    Likes:
    351

    With the work involved, even if the plug removal and installation is easy, I would simply put new plugs back in.

    Most manufacturers do not recommend anti seize compound on the spark plug threads in modern engines. Here is an interesting article: http://www.jagrepair.com/images/AutoRepairPhotos/NGK_TB-0630111antisieze.pdf
     
    06PTElectricBlue and AllanC like this.
  8. AllanC

    AllanC Well-Known Member

    Joined:
    Jan 6, 2003
    Messages:
    4,531
    Likes:
    1,122
    This is encouraging to know. So if you watch and inspect the plugs one should not have an issue with extended service life. The challenge will be how many additional miles you can get from the plugs. If you wait until performance problems surface or misfire occurs, you could damage and shorten the life expectancy of the catalytic converter.

    Good point. I did not realize that the same engine in the same model line could have different emission requirements and therefore spark plugs. Best to adhere to manufacturers specifications and type of plug.

    So this makes the point that you can push extended mileage intervals too far and create problems. Got to pay attention to what you are doing.

    Definitely learned something new with this article. Appreciate all who shared their comments.
     
  9. KOG

    KOG KOG

    Joined:
    Jan 8, 2003
    Messages:
    6,919
    Likes:
    434
    Not spark plugs, but using a thread locking compound on also alter the torque setting. I've not been able to find any specific values for how to compute this, but threads with locking compound will NOT have the same friction as either dry or lightly oiled threads. I've also caught tire changers (Wal Mart in this case) putting antiseize on lug studs and then tightening them to the same value specified for dry threads. When I called them on it they just said the their zone manger had told them to always put antiseize in lug studs or bolts. I showed them the FSM which stated very clearly the the torque setting they were using was for dry threads. A related issue is that so many of them use "torque sticks" on an air wrench to tighten lugs. I was a MAC tool dealer long ago and refused to carry those things on my truck because I had seen that the torque they would actually apply varied widely depending on the brand of impact wrench and the air pressure used. Only a bending beam wrench or a click which is in calibration should be used on lugs or any other fastener. I've heard that click type wrenches used to be banned in Chrysler engine labs because of their inaccuracy. I use them, but they should be calibrated by comparing them to a beam type wrench fairly often.
     
  10. DC-93

    DC-93 Well-Known Member

    Joined:
    May 1, 2014
    Messages:
    3,170
    Likes:
    2,067
    I don't remember seeing any bending beam torque wrenches in the Chrysler Engineering Motor Room. Maybe Fast Eddie will add his 2 cents.

    Just though of another good reason to change the plugs as stated. They may seize up in the heads.
    Metal plug versus aluminum head - different expansion rates.....

    how to remove stuck spark plug from aluminum head - Google Search (at https://www.google.com/search?q=how+to+remove+stuck+spark+plug+from+aluminum+head&sa=X&ved=2ahUKEwi05b7pgYTrAhUIR6wKHdDjBoEQ1QIoAHoECAoQAQ&biw=1333&bih=626#spf=1596628870398 )

    I have seen oil plugs that are difficult to remove because the owner used "extended" range oil.
    Back in the day, I remember a guy using a breaker bar to get an oil plug out. The owner "forgot" to change the oil, was only topping it off!!
     
  11. DC-93

    DC-93 Well-Known Member

    Joined:
    May 1, 2014
    Messages:
    3,170
    Likes:
    2,067
    Same applies for oil filters! I've seen them come apart, trying to get them off. All because they were left on too long.
     
  12. 06PTElectricBlue

    06PTElectricBlue Active Member

    Joined:
    Apr 2, 2019
    Messages:
    890
    Likes:
    1,016
    Each and every time that I've had any of my vehicles serviced, where the shop has removed the wheels, after I leave that shop, I pull around the corner and re-torque all the wheel nuts myself.

    First I back off each nut a very small amount, and torque to correct spec. There have been numerous times that I've had to stand on my breaker bar to loosen a lug nut, because some a**hole used an air wrench set too high. :eek:

    There was also one time while trying to loosen a lugnut that the stud started spinning. I went right back to that shop and showed them what they had done. They had to spend a couple of hours cutting off the lugnut. They tried to install another stud, but it wouldn't hold in the splines. They had to end up replacing the hub, all at their expense. :)

    But the moral of the story is, if I had not checked the lugnuts myself, and had been out somewhere and got a flat tire, with the spinning stud, there would have been no way that I would have been able to change that tire. ;)
     
    1999 White C5 Coupe likes this.
  13. KOG

    KOG KOG

    Joined:
    Jan 8, 2003
    Messages:
    6,919
    Likes:
    434
    I once had a shop leave all five lugs loose on one left wheel and it started unscrewing the nuts driving. Other shops have stripped stud on more than one occasion. Once had a shop lose one of the nuts on a 1T truck and just give it back to me missing the nut.
     
    06PTElectricBlue likes this.

Share This Page

Loading...
 We are not affiliated with FCA. We make no claims regarding validity or accuracy of information or advice. Copyright © VerticalScope Inc. All rights reserved.