http://www.agriculture.state.ia.us/biodiesel.html

"In blends over 20%, biodiesel has a solvent effect, which may release deposits accumulated on tank walls and pipes from previous diesel fuel. The release of deposits may clog filters initially and precautions should be taken."

Wouldn't it be reasonable to presume that a "tank cleaning" effect might still occur using soy-diesel blended at less than 20%, just slower and less pronounced?