My yard is 2 acres and I have it cut by a landscaper. Still have my 1989 MTD B&S mower from the last home we left in 1997. It has been sitting in my garage in the corner since then. Every once in a while over the past 12 years I would walk by it and just pull the starter cord to rotate the engine a bit. But the last time it ran was in 1997. I am now painting my garage and had to move it. So I poured a small amount of gas in it and pulled the cord once and it fired right up.. I let it get hot and then drained the very black 30w oil and refilled with ST 30w. Then I let it run for 15 minutes until it ran out of fuel. I was amazed that it started on the first pull. SO, I'll change the oil again in 2021. How's that for an extended OCI?