I have been pondering the actual purpose of the thread, and I don't know of a reason why one saw design would need a richer oil mixture than another. But I am pretty sure why newer saws go for a leaner ratio. I believe it is the oil available, not the saw. Most petroleum-based oils are basically a hydrocarbon with additives. Hydrocarbons are compounds of carbon and hydrogen with varying chain lengths. The simplest hydrocarbon, methane, has only 1 carbon, i.e., a chain length of 1. Ethane has 2, propane has 3, etc. As chains get longer, the oil is less volatile and more viscous. Commercial fuels and oils have mixtures of various chain lengths. Gasoline has an average chain length of 8. Kerosine averages 11. No. 2 diesel and heating oil averages 13. Engine oil can go quite a bit higher. When an oil is a mixture of varying chain lengths and exposed to heat, the more volatile, shorter fractions boil off, leaving reduced oil volume and a higher viscosity. Better oils have a more uniform chain length and do not change as rapidly in response to heat. In the case of 2-cycle oil, the lighter fractions flash off and are basically used as fuel, whereas the heavier fractions remain behind and do all of the lubrication. I would assume modern oils have been made with better control of chain length, allowing less oil to be used for the same net degree of lubrication. In the case of synthetic oils, the chain length is very close to uniform. The Chinese saw manufacturers may be using old oil ratios because of the practices that were often used years ago. If I were to buy a Chinese saw (not likely), I would not hesitate to use a 50:1 mix with a good synthetic oil regardless of what their manual says.
