Engine Oil Discussion

The factory recommended oil is 10-30 non synthetic., and that is what I use in all my slants. The only thing wrong with synthetic, is it will have a tendency to leak more, and is more expensive. I wouldn't worry about using added zinc, unless you have a fresh rebuilt engine. I would not use a straight grade oil, and definitely not SAE 50. If your engine needs SAE 50, it is time for a rebuild.