Wonder what's the difference between 2 cycle oil and non detergent SAE-30 crankcase oil? Years ago before "2 cycle" oil was available, SAE-30 crankcase oil was what was mixed with the fuel. So what's the difference? Is the actual 2 cycle oil less likely to separate from the fuel over time? The Lucas semi-synthetic oil I've been using is a 20 weight. The Opti-2 which I have used in the past is a 100:1 mix and is the equivilant to a 40 to 50 weight crankcase oil.