My wife’s 2003 Matrix, has 69000 miles on it, it runs beautifully, the spark plugs are good for 120,000 miles but the car is 15 yrs. old, should I spend $100 to have the plugs changed and maybe get a little better mpg or should I leave well enough alone??
If there were anything wrong with the spark plugs, the Check Engine light would be on with a misfire code.
Wait until 120,000 miles.
I am coming around to Tester’s thinking on this issue, and recently I removed and gapped and reinstalled the plugs on my 1999 Civic, instead of replacing them at the 35,000 mile interval I had followed since new.
They may become more troublesome to remove the longer they’re in there, but if done with care there’s probably only a small risk of damaging the threads in the cylinder head. If the carmaker’s advice is 120,000 miles and is not modified by a “or XX months, whichever occurs first” clause I think you’re safe to let it go. If curiosity gets to you first, remove one and look it over.
I replaced the plugs in my '06 Matrix at the 10 year mark and ~60,000 miles because I was concerned they might be difficult to remove.
They were reluctant and needed some back and fourth finesse.
There was no change in performance and the electrodes looked almost like new (irridium tipped).
They could have gone much further, but it’s a fairly easy DIY job, not expensive; and I felt pretty good afterward.