killingravensun said:

its pretty basic, getting raw material to make it from is the hard part, filtered used cooking oil is popular but hard to come by

once you have the oil you just need to process it, see: transesterification, which can be done using lye, lye can be made from running water through wood ashes, the lye separates the lipids from the oil, then you can use the fatty solids to make soap too

when soybean oil was cheap many years ago i would buy it new at a restaurant supply and put it straight into the tank of my diesel mercedes, ran it for about 20,000 miles before the price went up too high, no engine damage like some will tell you, in fact it cleaned out the gunk that was already in there, i have 390,000 miles on that engine and its still strong

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