We get a question here about how often should you service your small engine.
Walk behind mowers and small engines below 9hp - service air filter EVERY USE(clean it), change oil every 50 hours of use or at least once a year, change air filter and spark plug every 100 hours.
Riding Tractors and Zero Turn Mowers up to 30hp engines - service air filter EVERY USE(Clean it), change oil every 100 hours of use or at least once a year, change air filter, spark plug, and fuel filter every 100 hours.
Disclaimer: Always check your owners manual for your specific equipment. These times stated are a general estimate based on multiple brands of equipment.