Everyone knows the story of "The Little Engine That Could", but the engine powering your outboard motor or chainsaw is not going to do so well if the right type of two cycle oil is not used. It would be simple if all two-cycle engines were built the same, but they're not.
What Is A Two-Cycle Engine?
A two-cycle (or two-stroke) engine is an internal combustion engine which the thermodynamic cycle is completed in two pumps of the piston. This gives it a distinct sputtering sound. These lightweight engines' crankcases are not closed, they are part of the induction tract and in order to keep them lubricated oil has to be mixed with the regular gasoline. This combination of oil and gas in the induction tract causes exhaust that has a blue tint to it and a very oily scent.
Two-cycle engines come in two distinctly different types. First is the water-cooled two-cycle engine, exemplified in most outboard motors. These engines have a high output demand. They are usually set at a high speed which is maintained for extended periods of time and they have a continuous flow of water passing through them to cool them. Then there is the air-cooled two-cycle engine. Air-cooled two-cycled engines, such as chainsaws and weed whackers, have a much different operation life. They are constantly being started and stopped and different demands on engine output are being made depending on the item the saw or other tool is being used on. It is the differences between these two engines, how they operate and the demands placed on their systems that determines the kind of two-cycle oil you will need to choose.
Why Two-Cycle Oil?
In order for a two-cycle engine to run properly, the gas has to be combined with oil for lubrication. Common sense would say that any sort of lubricating oil would work, but there is a problem. Regular lubricating oil has a high ash content, which can become a serious problem when it is burned in the engine's combustion chamber. Two-cycle oil has a lower ash content so it will not build up as much of a deposit. Comparing 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 minimizeize deposits that tend to form if ash is present in the oil which is burned in the engine's combustion chamber. But not all two-cycle oils are created equal. The kind of two-cycle oil you choose will depend primarily on the kind of two-cycle engine you are using.
What Kind of Two-Cycle Oil?
Technically there are three kinds of two-cycle oils. One kind is specifically formulated for water-cooled two-cycle engines. A second kind is configured for air-cooled two-cycle engines. The third is supposed to be multi-purpose, that is, usable in either air or water cooled engines. Keep in mind however, that if you switch oils – even between brands, say from multi-purpose to air-cooled, you should completely drain the old oil before adding the new oil due to the differences in formulation and consistency.
Selecting the correct two-cycle oil for the type of engine you are using can significantly improve your engine's performance.