i have not had any problems like you seem to be having. while researching veggie oil i read that there is a gasket between the fuel pump and the block that can go bad and start pumping your motor full of fuel or what ever your using for fuel, i have no idea of knowing if this is true or not but the guy who posted it was a senior member of the club and seemed very knowledgable about 6.9's. i don't know what delo400 oil is so i can't help you there, but i've been getting my oil from a local shop and i'm sure there have been blends of all kinds of oil in it. check out this guys webpage www.hartshangout.citymax.com and frybrid.com, frybrid is where i found the post about the fuel pump issue