Using the information you have provided and not visually inspecting the roof, the black spots on your roof are more than likely algae. Most shingle manufacturers use copper or zinc coated granules to aid against the growth of algae.
Two-stroke oil (also referred to as two-cycle oil, 2-cycle oil, 2T oil, 2-stroke oil or petroil) is a special type of motor oil intended for use in crankcase compression two-stroke engines.omparing regular lubricating oil with two-stroke oil, the relevant difference is that two-stroke oil must have a much lower ash content. This is required to minimize deposits that tend to form if ash is present in the oil which is burned in the engine's combustion chamber.
2-Cycle Engine 40:1 Mixture Ratio Information Unlike four-cycle engines that have a separate oil reservoir for lubricating the engine, two-cycle engines are lubricated through the combustion cylinder by mixing specially formulated oils with the fuel.our 3.2 oz pre-measured amount of 2-cycle engine oil into a clean gasoline container. 3. Add 1 gallon of gasoline to the 3.2 oz oil. 4. Seal the gas container and gently swish it until the oil completely mixes.