Originally Posted by ccs368
For my H4 non turbo engine, I replaced the four factory OEM NGK spark plugs Subaru p/n 22401AA65A or FRP5AP-11 with the identical plugs at 125k. These NGK platinum tips are rated at 90K. The tips on two of them eroded from .043 gap to .071 gap. The factory manual recommends 60k intervals and based on my findings, I would change no later than 90k for my application the next time. The odd thing is there were no check engine lights or signs of misfiring or significant loss of mpg. I'm usually around 25mpg with mixed driving or 27mpg in the summer.
60k may not be bad advice because the tube seals also tend to harden up and let oil traces inside and could cause shorts from the ceramic insulator to the boot. Estimated time to replace plugs was about 1.5 hours or less if I rushed but you just need to have the right combination of extensions and patience to do the job.
Which year? My non turbo h4 also has those plugs, and Subaru says to replace the plugs every 30k.
For my H4 non turbo engine, I replaced the four factory OEM NGK spark plugs Subaru p/n 22401AA65A or FRP5AP-11 with the identical plugs at 125k. These NGK platinum tips are rated at 90K. The tips on two of them eroded from .043 gap to .071 gap. The factory manual recommends 60k intervals and based on my findings, I would change no later than 90k for my application the next time. The odd thing is there were no check engine lights or signs of misfiring or significant loss of mpg. I'm usually around 25mpg with mixed driving or 27mpg in the summer.
60k may not be bad advice because the tube seals also tend to harden up and let oil traces inside and could cause shorts from the ceramic insulator to the boot. Estimated time to replace plugs was about 1.5 hours or less if I rushed but you just need to have the right combination of extensions and patience to do the job.
Which year? My non turbo h4 also has those plugs, and Subaru says to replace the plugs every 30k.