Drawn to true relative scale — the variants above are directly size-comparable.
Spark plugs
Look down the bore at the centre electrode. A hair-thin wire pin standing proud is iridium; a flat shiny disc flush with the electrode face is platinum; a plain blunt nickel post is worthless. A matching disc on the underside of the ground strap means double-platinum.
How to spot it
14 or 16 mm hex, threaded, ceramic insulator stamped NGK, Denso, Bosch, Champion or Autolite. Brand codes give it away: NGK IFR/LZFR and Denso IK/IT/FK are iridium; NGK PFR and Denso PK/PT are platinum. Four to sixteen per engine, under the coil packs on the cylinder head.
Metal content
| Metal | Quantity | Notes |
|---|---|---|
| Platinum | 1–8 mg per plug | pad on the centre and sometimes ground electrode |
| Base metal | iridium 0.6–3 mg on Ir plugs | iridium has no daily spot price; roughly $0.56 of metal |
At 4 Aug 2026 spot prices that works out to $4.42 per pound of contained metal — Platinum 0.08 g = $4.42. A refiner paying $0.08 returns about 2% of that, which is normal: refining costs money and the buyer takes a margin.
Safe removal
Working temperature: Cold engine only
Engine cold — aluminium heads strip when hot. Blow the plug wells out with compressed air first, then a 5/8" or 13/16" plug socket with the rubber retainer, extension and swivel. Ford Triton 3V plugs are two-piece and notoriously break; not worth the fight for scrap.
Hazards
NEVER short a large capacitor with a screwdriver. It welds the tip, blasts molten metal at your face, and can rupture the can.
NEVER grind, sand, saw or incinerate anything that might contain thorium or radium. Sealed sources stay sealed.
Don't rush a hot engine. Nothing here is worth a hand.
Before you scrap it
The common trap
Questions
How much gold is in spark plugs?
Platinum: 1–8 mg per plug. At current spot that is about $4.42 of contained metal per pound.
How do you identify spark plugs?
Look down the bore at the centre electrode. A hair-thin wire pin standing proud is iridium; a flat shiny disc flush with the electrode face is platinum; a plain blunt nickel post is worthless. A matching disc on the underside of the ground strap means double-platinum.
How do you remove spark plugs safely?
Engine cold — aluminium heads strip when hot. Blow the plug wells out with compressed air first, then a 5/8" or 13/16" plug socket with the rubber retainer, extension and swivel. Ford Triton 3V plugs are two-piece and notoriously break; not worth the fight for scrap.
Is spark plugs worth more working than as scrap?
Only aviation fine-wire plugs matter — a real overhaul-core market at $30–150 each against essentially zero as scrap, because their electrodes carry 50–200 mg of platinum group metal. Everyday used automotive plugs have no resale.
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