yes, I ran a tank or two of B20 before I ran it on SVO. I just put the SVO straight in the tank and blended it with dinodiesel usually about 4/1 mix but sometimes as much as 1/1. It ran great in the summer until the problems started. I did filter the SVO really well.
My next move is to drop the tank, and clean it out really well, blow out the fuel lines, and clean the strainer. Ill go from there...