I bought an old tractor this spring. Upon further investigation,1 cylinder was about 60 lbs low on compression. After a leakdown test,I concluded the rings were carboned up. It was either re ring it,or try something else. I ran seafoam in the oil for about 2 hrs. Then drained the oil and changed it. Compression is identical on all cylinders now,and has been running like a top all summer.