Please tell us more about this! Here are my questions: 1) Are you burning pure soy oil or mixture? Ratio? 2) Where do you buy the soy oil? 3) How much does soy oil cost per gallon? 4) How does soy oil mileage compare against regular diesel oil?
I am using 100% soy biodiesel. Around here it is costing $3.67/gallon, although I get a 50% rebate from the Maryland Soybean Board. I buy it at a gas station. My mileage is the same (22city/27hwy).
In another part of the state, it runs about the same as regular diesel....go figure (about $2.50/gal).
Biodiesel does not require any engine mods, however, you need to keep an eye on your fuel lines. The older pure rubber ones will start to weep over time. You then replace them with Viton type lines.
In the winter, I can mix pure biodiesel with 20% kerosene to keep the pour point low enough for the cold weather. The gas station does winterize it (add kerosene).
Check out this website for Texas biodiesel sales:
http://www.nbb.org/buyingbiodiesel/retailfuelingsites/showstate.asp?st=TX