So I was thinking. It has been at least 10 years, probably closer to 12 years, since I changed the oil in my mower. Got it in 2000. Used 1 hour per week from April-November. I know it had Mobil 1 5w30 last change. Up until the last time, I would change it every season. [censored] thing still starts first pull, two after sitting the winter. Craftsman with a Briggs, 6.5 HP. Could probably use a blade sharpening, never had one.