When adding power adders like a supercharger or turbo you need to correct the spark plug heat range to optimize how you Mustang runs. Fits 2005-2008 3V heads requiring the 16 mm thread
- For use in engines with higher than stock cylinder combustion pressures or sustained high rpm
- Unique design is proprietary to Ford 3-valve engines
- One heat range colder than the stock Mustang GT plug
- Two heat ranges colder than the stock 5.4L-3V truck engine plug
- Sold in engine sets of 8
- Use M-12405-3V12MM spark plugs for 2008 and newer 3V heads
- Note:
- 2008 engines with late style 12 mm spark plugs can be identified by coil engineering number 8L3E
- 2005-2008 engines with early style 16 mm "High Thread" design spark plugs can be identified by coil engineering number 3L3E part number
- All 2009-2010 engines use 12 mm spark plugs
- **This part supersedes Ford Performance M-12405-3V0**
