I've been using Soy Ultra. It is for continuous usage. Working well...very good gas mileage and very clean spark plugs after 30k. I'm switching to FP-Plus...easier for me to get. Once every couple of years a buddy and I combine for a big order from Schaeffer (free freight), and I don't get myself organized to get the fuel treatment at the right time.
The uses for methyl soyate include printing ink removal, paint stripping, metal degreasing, oil spill clean-up and resin removal. Numerous consumer products also are based on methyl soyate including hand cleaners, body lotions, car waxes and safe household cleaners.
I think it it's probably closer to Redline SI-1 or Amsoil PI than Techron/Regane or Lucas.