Best spark plugs

Start with NGK Iridium IX. Iridium fine-wire tips last far longer than copper or plain platinum and hold their gap, so it's the safe default for most daily drivers — and it's the cheapest way into a premium plug here.

Who the others suit:

• NGK G-Power (platinum) — budget-minded owners of older cars who change plugs on schedule anyway.
• DENSO Iridium Power IK20 — Japanese engines where you want OE-style iridium; check your thread reach and gap first.
• Champion / ACDelco double platinum — GM and Chrysler-family cars that came with platinum from the factory.
• A-Premium 6- and 8-packs — a full set in one box for V6s and Ford V8s.
• HKS M45XL — tuned or turbo cars needing a colder heat range.

Match the plug number to your engine before buying; heat range and reach matter more than brand.