I actually just found the article...
it is in the new Soundings (july), the stuff they talk about is called B-20 and is 80% diesel and 20% soy, and is only 8 cents more per gallon. There is a guy that uses 100% soy and it does say that the pure soy can soften hoses and seals like you said. The b-20 seems like the way to go though, it emits 38% less NO2, 74% CO, and 100% less smoke, as well as acting like a solvent to clear up carbon build-up. It also has a higher ingnition temp so it is more efficient. BTW, I don't work for the maker of B-20, But I do work for an environmental engineering firm and wish that my local marina would carry the stuff, nothing worse than smelling diesel fuel! Popcorn anyone?