I have a self-propelled 22" mower with a 6.0 HP B&S Intek engine. Last year I had to have it worked on. The mechanic said a valve was burned and frozen. I believe it was over $100 for repair. This mower was used for the first 6 years to cut about 0.15 acres. For the last 3 years it is only used to cut the levy on my pond (new house/yard). However, the levy is 30 - 40 degrees. I mow with the discharge away from the water which means the dipstick is on the low side of the mower. Yesterday, I noticed the engine sounded different when I was at an angle (more tinny). I'm wondering if this is a lubrication issue due to the angle. Do I need to switch to a synthetic for better lubrication at an angle? Do I need to do anything different? I have to have a self-propelled unit and don't really want to buy another mower for quite some time - thus I want to make sure this one keeps working. I've tried a string trimmer but the area is too large for me to do that way. If I need to change oils, is a full synthetic better for this? The mower is used about 1 hour every 2 weeks or so.