I've struggled with this answer since I'm not a biologist or biochemist. Perhaps another tutor will add something to my post. Corn oil and olive oil are processed to rid them of toxic materials AND they are much much heavier (more dense and more viscous) than diesel oil or diesel fuel. When I think of diesel fuel I think of something like kerosene. No one in their right mind would drink kerosene. The biodiesel fuels are processed, also, BUT they are distillates of crude oil that comes off at much lower temperatures. For example, the boiling point of kerosene is about 150 C while that of soy oil used for cooking is about 300 and most other oils (corn oil and olive oil) are higher than that. So why don't we drink kerosene or gasoline? They are mixtures of a boiling range that contains hydrocarbons, benzene, xylenes, etc that are known to be carcinogenic. Ingested as a liquid I think they are such non-polar compounds that the human body simply can't digest them. They damage the intestinal tract, the lungs, the kidneys and anything else they come in contact with. Cooking oils, on the other hand, are much higher molar mass, they don't have nearly the extraction possibility of the lower boiling point gasoline/kerosene, they react slower, and the body can handle them as it does any food. I hope this helps. If you want more information, you may want to go to www.google.com and type in key words such as toxicity gasoline, edible oils, etc. To repeat myself, perhaps another tutor will care to add his/her musings.