You should replace the spark plug in your snow blower at least once every season or after approximately 100 hours of use, whichever comes first. Regular maintenance is crucial for optimal performance and longevity of the machine. Over time, spark plugs can become fouled with carbon deposits, oil, or fuel residue, which can lead to poor engine performance, difficulty starting, or increased fuel consumption. 
Inspect the spark plug at the beginning and end of each season. Look for signs of wear such as a worn electrode, cracks in the porcelain insulator, or heavy carbon buildup. Even if the spark plug appears to be in good condition, replacing it annually is a good practice to ensure reliable operation. 
If you experience issues like hard starting, misfiring, or a noticeable drop in power, check the spark plug as it might need replacement sooner. Always refer to the snow blower’s owner manual for specific recommendations regarding spark plug type and replacement intervals, as these can vary by model and manufacturer. 
Using the correct type of spark plug is essential. Ensure that the replacement spark plug matches the specifications provided by the manufacturer, including the correct gap setting. Proper installation is also important; avoid overtightening, which can damage the threads or the plug itself. 
Regularly replacing the spark plug is a simple and cost-effective way to maintain your snow blower’s efficiency and reliability, ensuring it is ready to tackle heavy snowfalls when needed.