My father in law gave me an old rear tine tiller that has been setting for 3 years. After cleaning it up and replacing the gas lines and belts it is running. I've never owned one so I was wondering what maintenance is usually required. It is a 5hp briggs 4 cycle engine and says it was manufactured for the CO-OP, but the serial numbers aren't legible. I'm going to change the oil and sparkplug today. What type of oil do I use? Any other recommendations.