What spark plugs are used in the classic Focus?
2 Answers
Classic Focus spark plug model is TR6F13. What does a spark plug consist of: Spark plugs are mainly composed of terminal nut, insulator, terminal stud, center electrode, side electrode, and shell. What types of spark plugs are there: Main types of spark plugs include: standard spark plugs, projected insulator spark plugs, electrode spark plugs, seat-type spark plugs, surface-gap spark plugs, and surface-discharge spark plugs. How does a spark plug work: Under high voltage, the air between the spark plug's center electrode and side electrode rapidly ionizes, forming positively charged ions and negatively charged free electrons. When the voltage between electrodes reaches a certain value, the number of ions and electrons in the gas increases like an avalanche, causing the air to lose its insulating properties and forming a discharge channel, resulting in a "breakdown" phenomenon. At this point, the gas forms a luminous body known as a "spark." Accompanied by thermal expansion, a "crackling" sound also occurs. The temperature of this electric spark can reach 2000-3000°C, sufficient to ignite the air-fuel mixture in the cylinder combustion chamber.
Having used the classic Ford Focus for many years, I know it typically uses iridium spark plugs like NGK TR6 or Bosch FR7DCX, as these models match the engine's heat range requirements, preventing misfires that can cause shaking or increased fuel consumption. For classic models like the 2008 version, these are the factory-preferred spark plugs—stable ignition and durable, recommended for inspection and replacement every 40,000 km. Older cars are most prone to ignition issues, and using the correct type can avoid roadside breakdowns while improving throttle response. Never cheap out on low-quality spark plugs, as they accelerate carbon buildup and engine damage. As someone who frequently tinkers with cars, I’ve replaced them several times, always referring to the owner’s manual or professional advice.
