How often should spark plugs be replaced?

Copper: every 30,000 miles. Platinum: every 60,000 miles. Iridium: every 80,000–100,000 miles. Replace sooner if you notice misfires.

Can bad spark plugs cause a check-engine light?

Yes — worn plugs cause misfires that trigger P0300–P0308 codes and can eventually damage the catalytic converter.

Should I replace ignition coils when I replace spark plugs?

Not necessarily, but inspect them. If a coil shows cracks or corrosion, replace it while you have access.

Buyer Guide

Best Spark Plugs

Spark plugs are one of the most impactful maintenance items for engine performance. Worn plugs cause misfires (P0300–P0308), rough idle, poor acceleration, and reduced fuel economy. Replacing them is one of the easiest DIY engine jobs.

Run Free Maintenance Scan Explore Marketplace

What to look for

Material — iridium lasts longest (60K–100K miles), platinum is mid-range, copper is cheapest but wears fastest
Heat range — must match your engine's specification; too hot causes pre-ignition, too cold causes fouling
Gap — most modern plugs are pre-gapped, but always verify with a feeler gauge against your vehicle spec
Thread size and reach — incorrect dimensions will not seat properly and can damage the cylinder head
OEM recommendation — your owner's manual specifies the exact plug type, gap, and material

Our picks

Editor's Choice

NGK Iridium IX Spark Plugs

Best Overall

$8–$14 each

4.7/5

Industry standard iridium plug — excellent longevity, wide vehicle coverage, and reliable performance

Check price on Amazon

Verify this part fits your exact year, make, and model before buying.

Denso Iridium TT Spark Plugs

Best for Japanese Cars

$7–$12 each

4.6/5

Twin-tip iridium design for better ignitability — OEM choice for many Toyota and Honda engines

Check Price

Bosch Platinum+4 Spark Plugs

Best Mid-Range

$5–$9 each

4.3/5

Quad-electrode design for consistent spark — good mid-price option for older vehicles

Check Price

Champion Copper Plus Spark Plugs

Best Budget

$2–$5 each

4.1/5

Best budget option — ideal for older engines that specify copper plugs

Check Price

As an Amazon Associate, ratchit Automotive Solutions earns from qualifying purchases. Verify fitment before purchase.

Buying tips

Buy the plug material your owner's manual specifies — upgrading from copper to iridium on an engine designed for copper offers marginal benefit
Replace all plugs at once — mixing old and new creates uneven combustion
Apply a thin layer of anti-seize to threads (unless the plug has a factory-coated thread)
Torque plugs to spec — over-tightening strips aluminum heads; under-tightening causes leaks

Related diagnostic codes

P0300 P0301 P0302 P0303 P0304

Related guides

Best Ignition Coils Best Obd2 Scanners

Related OBD-II code guides

See the codes this part commonly triggers — and what to inspect before replacing anything.

Recommended tools & parts

These recommendations appear because this issue commonly requires inspection in this system area. ratchit does not recommend replacing parts until the likely cause is confirmed.