The frequency of replacing spark plugs depends on the type of spark plugs, vehicle make and model, and driving conditions, but general guidelines are as follows:

• Most modern spark plugs, especially platinum or iridium types, should be replaced approximately every 100,000 miles (about 160,000 km)

• Some vehicles recommend replacement intervals ranging from 30,000 to 90,000 miles depending on the specific model and spark plug type. For example, a Toyota Corolla may require spark plug changes every 60,000 miles, while a Toyota Sienna may go up to 120,000 miles before replacement is needed

• The quality and type of spark plug affect lifespan, with some lasting as little as 20,000 miles and others up to 150,000 miles

• If the vehicle is driven frequently in stop-and-go traffic, tows heavy loads, or uses poor-quality fuel, spark plugs may wear out sooner and require earlier replacement

Signs that spark plugs need replacement before the recommended mileage include:

• Rough idling or engine misfires
• Slow acceleration or sluggish engine performance
• Difficulty starting the engine
• Check Engine light illumination
• Poor fuel economy

It is best to consult your vehicle’s owner’s manual for manufacturer-specific recommendations and have spark plugs inspected regularly by a mechanic during routine maintenance

. In summary, replacing spark plugs every 30,000 to 100,000 miles is typical, with many modern vehicles extending this interval to around 100,000 miles, but individual conditions and vehicle specs may require adjustments.