I'll echo what Don said, welcome to FTE. The 6.0L in your Excursion will burn biodiesel just fine, you might notice a slight change in fuel mileage...and if your burning a high enough ratio (B20 and up) your exhaust will definitely smell different. And if you've got allot of miles of dino-diesel, maybe a clogged fuel filter as the biodiesel cleans the trash out of the fuel system. I started running B20 through my truck with 30k on the odometer and didn't have any issue with clogged filters.