Although I agree that anything more then 8% oil content is a waste. But the more oil content in the oil does not cause your enigne to run lean. Running lean is due to not enough fuel to the air mixture, and not the oil escaping from the exhaust. Now some noobs can over lean an engine due to having high oil content (the fuel) does not offer as much power, so they tend to lean it out till they get the power they want. Now they have a lean running engine that still spits out as much smoke as a race blend fuel does. And running it lean causes premature wear and kills the engine. But the engine does not run lean due to the oil not coming out of the exhaust, it's due to not enough fuel for the amount of air that is being introduced to the engine.