Copper plugs often need replacing around 30,000 miles, while platinum and iridium plugs commonly last 60,000 to 100,000 miles. Your owner's manual gives the exact interval for your engine.
Key takeaways
- Copper wears fastest.
- Iridium lasts longest.
- Replace coils if weak.
Plug types
Copper conducts well but wears. Platinum and iridium resist wear.
Signs of worn plugs
Rough idle, hesitation, poor mileage and misfires.
Replacing them
Torque matters. Over-tightening damages threads.
Check the coils
Weak coils shorten plug life.
Smog link
Worn plugs can fail a test.
Gapping and torque
Spark plugs must have the correct gap and be tightened to the right torque. Too little torque lets the plug overheat, and too much can strip the threads in an aluminum head. Many modern plugs come pre-gapped but still need to be checked. A technician uses a torque wrench and an anti-seize compound only if the plug maker allows it.
Coil boots and wires
A new plug in an old coil boot can still misfire if the boot is cracked or oil-soaked. Many shops replace boots or coils when they replace plugs on engines with known weaknesses. Ask whether your engine has a history of coil failure. Replacing a cheap boot now can avoid a second visit.
Plugs and smog
Worn spark plugs raise hydrocarbon and carbon monoxide readings and cause misfires that damage the converter. Replacing them on schedule is one of the cheapest ways to protect a smog pass. If your car is near a plug interval and your smog check is coming, do both in the same visit. Keep the old plugs for the technician to read, because their wear pattern tells about fuel mixture and oil use.
Need help in south Bakersfield?
Questions about maintenance & oil change? Read our Maintenance & Oil Change page, call (661) 599-9098 or request a time. Peña's Auto Electric, Smog & Repair, 303 Taft Hwy, Suite B, Bakersfield, CA 93307. Mon to Fri 9:30 AM to 5:30 PM, Sat 8 AM to 1 PM.
Frequently asked questions
How often should plugs be replaced?
Per type and manual.
Can old plugs cause a misfire?
Yes.
Do I replace all at once?
Yes.
Can plugs hurt gas mileage?
Yes.