That is where you are miss informed. In the context of what you are talking about a two stroke burns cleaner, because of the oil in the mix, because it burns hotter, therefore it burns more completely.
No oil is left un burnt.
The by product of the oil in the old days was microscopic ash and carbon. Those things are typical of the tripe that the ignorant gre enies dribble, even to this day.
Another factor in the efficiency of the engine is that in a one cylinder example the two stroke has only three moving parts. The four stroke has dozens of moving parts and friction is a huge consideration in energy losses as evidenced by the latest engines using zero weight oil.
In fact the only engine that is more efficient than the latest two strokes is a formula 1 mega dollar race car engine, and even that is only a few % better that the production two stroke which by the way are used in all of the largest ships travelling the globe every day and as we all are aware when money is involved and you burn tonnes and tonnes of fuel per hour, only the most efficient systems are used.
