Dale-
Biodiesel is a blend of vegetable oil usually made from soy beans and petroleum diesel with maybe a 80 diesel-20% bio ratio. It is suppose to be cleaner burning as it has no sulphur compounds. Willie Nelson has been using it for quite some time in his tour bus and swears by it. Do a Goggle search and you can find considerable info on the net. In the mean time here is a link:
http://www.nbb.org/resources/biodies...s/default.shtm
If you use it let us know what the results are. You might want to talk to GM first and make sure you will not void any warranty. As far as I know it is not available in Texas.