As long as users understand the risks of using biodiesel, take the proper precautions, and have a good quality source, the risks are low. If you have been using B10 successfully over a period of time in your International engines, I wouldn’t discourage you from trialing B20. Many fleets are running B20 with very few issues.
That said, International cannot expressly endorse blends higher than B5, because there are insufficient specifications for the blended fuel. Use does not void the warranty per se, but if use of biodiesel is shown to be the cause of a failure, than that failure is the responsibility of the user or fuel supplier. The same would be true in the case of failures caused by any fuel or additive.
Poor or inconsistent quality tends to be the number one problem with biodiesel. We recommend that anyone wanting to use biodiesel seek out a source of supply that has BQ9000 certification from the biodiesel board. The biodiesel board website, www.biodiesel.org, is an excellent source of information on how to successfully use biodiesel in your fleet.