The 5.7L HEMI V8 is one of the most beloved American engines of the modern era — powerful, torquey, and distinctive. But it has a spark plug situation that catches first-time owners off guard: it uses two plugs per cylinder, for a total of 16 spark plugs.
Why 16 Spark Plugs?
Chrysler's second-generation HEMI uses a dual-spark design originally developed for emissions compliance. Two plugs per cylinder allow more complete combustion of the fuel mixture, which reduces emissions and improves efficiency. Each cylinder has a primary plug (larger) and a secondary plug (smaller).
Which Plugs to Use
Champion Iridium plugs are the OEM-preferred specification for the 5.7L HEMI. They're available in the correct specifications for both the primary and secondary positions. NGK Iridium IX is an excellent alternative.
Part numbers vary by model year — the 2009+ HEMI uses different plugs than the 2003–2008 version. Always verify by year, make, and model before purchasing.
Service Interval
Chrysler specifies 30,000 miles for the HEMI's spark plugs — shorter than many modern engines. With iridium plugs, some owners stretch to 40,000 miles, but staying closer to 30,000 is advisable given the dual-plug system complexity.
Cost of a HEMI Tune-Up
With 16 plugs, the parts cost is double a normal 8-cylinder engine. Budget for two full sets when pricing out your tune-up — but the parts are straightforward and the job is very DIY-friendly with patience.
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