With the growing acceptance of biodiesel, the fuel has become more available and standards are being created to make sure that all biodiesels are created equal. With some of those hurdles being overcome, manufactures are able to do a better job of testing and ensuring that their engines will operate on biodiesel blends with a higher concentration of renewable fuels. Cummins has done exactly that
, and has announced that their 2002 and later emissions-compliant ISX, ISM, ISL, ISC and ISB engines are now certified for biodiesel blends up to B20, up from the previous B5. I would expect more of this type of announcement in the future.
[Source: Renewable Energy Access]