I think the 16:1 number comes from less developed countries where they use cruder types of oil for the mix (think non-detergent 30 weight). I used 20:1 with fossil oil for the first 2 gallons, 25:1 with fossil oil for the second 2 gallons and then went to 30:1 with a good quality synthetic oil. The theory is that the fossil oil doesn't reduce friction as much and allows the engine to wear in properly. Then after it is broken in you switch to the synthetic oil that reduces further wear. Just what I've picked up hanging around here.
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