Biodiesel Myth #7 – Biodiesel is Just Vegetable Oil

In a multi-part series about biodiesel, this is one of several articles in an attempt to dispel the myths about biodiesel and it’s use in commercial and private diesel engines.

Myth #7 – Biodiesel is Just Vegetable Oil

This is one of my favorites, mostly because for a long time the media simply wouldn’t actually spend the 10 minutes online researching the difference between soybean oil and biodiesel to know the difference, and actually perpetuated this myth more than anyone else.

To the layman, I can see why it’s easy to confuse.  Rudolf Diesel first invented his engine to run on Peanut oil, as many reporters accurately claim.  However, the modern engine looks almost nothing like Rudolf Diesel’s engine, and that while it’s true that many modern diesel engines can run straight vegetable oil, almost none do because it’s generally accepted as harmful to the engine in the form of engine coking and fouling.  Using vegetable oil also require significant pre-heating of the fuel and a complicated dual fuel setup which is beyond the scope of this blog article.  See the Elsbett SVO Conversion (which will void your warranty) diagram for an idea of just how complicated these systems can be.  For more information, Google “Diesel SVO Conversions” and you’ll see what I mean.

SVO Conversion Diagram

I’ll say it once more in more simple format: “Straight Vegetable Oil Is Not Biodiesel“.

So, what do biodiesel and straight vegetable oil have in common?  Biodiesel is quite usually made from vegetable oil.  But, in truth, biodiesel can be made from animal fats too, or most any fat, for that matter.  Through a process called transesterification, vegetable oil is stripped and converted into Biodiesel (which is technically called a mono-alkyl ester).  This new chemical, trade named “Biodiesel”, is now more chemically similar to petroleum diesel, and has many of the same characteristics of it’s petroleum cousin.  Biodiesel is registered motor fuel and approved by the EPA as a motor fuel and fuel addative, and has an ASTM standard (D-6751) which must be adhered to in order to sell it as a motor fuel.  This standard has very tight requirements on the composition of the fuel, and the limits on impurities that can exist in that fuel.  Fuel that does not meet the standard cannot be sold as biodiesel for motor fuel use.

Vegetable Oil doesn’t have any of those standards and approvals.   See, vegetable oil is generally used as food. Biodiesel is fuel. More to the point, because SVO is not an approved motor fuel by the EPA, using it will most certainly void the engine warranty.  You can actually see the difference.  The picture below shows straight vegetable oil on the left, and biodiesel on the right.  Both are filtered, clean products that could be used as a motor fuel.  The difference is in the viscosity, gums, combustibility, and cold weather performance.    Which one would you put in your engine?

SVO vs. Biodiesel