Free repair checklist
Free Spark Plug Guide — Restore Lost Power and MPGs in an Afternoon
Worn spark plugs cost you fuel economy and acceleration every mile. This guide shows you how to replace them yourself and get back the power your engine had at 30,000 miles.
This checklist is a practical starting point. The DIY Mechanic System gives you a clearer path to diagnose the problem, plan the job, and complete the repair.
What this checklist covers
- How to identify the correct spark plug spec (heat range, gap, electrode type) for your engine
- The exact torque spec — and why over-tightening is worse than under-tightening
- How to use a feeler gauge to gap plugs correctly (most pre-gapped plugs are wrong)
- How to read a used spark plug: what carbon fouling, oil fouling, and overheating look like
- The difference between copper, iridium, and platinum plugs — and when each is worth the price
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