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3-second answer: Plugs: copper or double-platinum, gapped 0.054 in (5.0/5.8/7.5) or 0.044 (4.9 I6). Torque: 10-15 ft-lb (5.0/5.8 typically 15). Do the wires, cap, and rotor while you're in there — 30-year-old wires are the real misfire cause. The 5.8's #4 and #8 plugs (rear, driver side) need a swivel socket and patience.

The plan

  1. Which plugs: copper (cheap, fine, 30k miles) or double-platinum (60k+). Don't buy the fancy iridium for a stock 5.0 — it's wasted money.
  2. Gap: 0.054 for the V8s, 0.044 for the 4.9. Check with a feeler gauge — pre-gapped plugs drift.
  3. Order: do one wire at a time so you don't cross the firing order — the #1 mistake (especially on a 5.8, which differs from the 5.0).
  4. The 5.8 rears: #4 and #8 are against the firewall — a swivel spark plug socket + extension (and maybe dropping the dipstick tube bracket) is the trick.
  5. Anti-seize: a light coat on the threads (don't over-torque to compensate).

Torque

Engine Plug torque
4.9 I6 10-15 ft-lb
5.0 / 5.8 / 7.5 10-18 ft-lb (15 typical)

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